The Effectiveness and Safety of Dupilumab for the Treatment of Recalcitrant Chronic Actinic Dermatitis: A Case Series.

Background: Although dupilumab is an effective treatment approach for chronic actinic dermatitis (CAD) in some cases, its effectiveness and safety in CAD have not been sufficiently assessed. Purpose: Evaluation of the effectiveness and safety of dupilumab in patients with recalcitrant CAD was performed. Methods: We retrospectively reviewed the medical records of CAD patients treated with dupilumab. Data regarding demographics were collected, and disease severity scores were assessed using the following: Clinical Severity Score of CAD (CSS-CAD), Atopic Dermatitis Control Tool (ADCT), Dermatology Life Quality Index (DLQI), and Numeric Rating Scale (NRS)-itch scores. Results: After 12 weeks of treatment, there was a significant decrease in disease severity scores of 16 CAD patients. Only one patient achieved a good response and most of the patients (62.5%, 10/16) had no significant symptom improvement after 4 weeks of treatment. However, after 12 weeks of treatment, 43.75% (7/16) of the patients reached excellent response (>75% improvement of CSS-CAD), 31.25% (5/16) good response (50%-75% improvement of CSS-CAD), 6.25% (1/16) partial response (25%-50% improvement of CSS-CAD), and only 18.75% (3/16) no response (<25% improvement of CSS-CAD). One patient complained of injection site reaction at the first injection. Conclusion: This study supports dupilumab as an effective and safe treatment option for patients with recalcitrant CAD. Patients may require at least 4 weeks of treatment before the partial response is noted.

HIV-associated photodermatitis in African populations.

Photosensitive dermatoses are seen in 5% of HIV-infected persons. These include drug- and chemical-induced photoallergic and phototoxic reactions, chronic actinic dermatitis of HIV, photo lichenoid drug eruptions, and porphyria. Data on photodermatitis in HIV are limited to case reports and series. The pathogenesis is not completely understood and includes a th2 phenotype in HIV which results in impaired barrier function and resultant allergen sensitisation as well as immune dysregulation. The objective of this manuscript is to review the literature on the clinical phenotype, pathogenesis, role of photo and patch testing, outcomes, and treatment of photodermatitis in HIV in an African population.

Variable Presentations of Photodermatoses - A Case Series.

Photodermatoses represent a broad spectrum of skin diseases caused because of exposure to ultraviolet radiation. It is categorized mainly as idiopathic photosensitive disorders, drug or chemical induced photosensitivity reactions, DNA repair-deficiency photodermatoses and photoaggravated dermatoses. Despite being under the photodermatoses umbrella, the pathophysiology of each type of photodermatoses varies. We reported 4 cases of photodermatoses including azathioprine induced pellagra, adult onset actinic prurigo, and photoallergic contact dermatitis due to NSAIDs and cutting fluids. Photoprotection with the usage of photoprotective clothing, broad-spectrum sunscreen application and avoidance of photosensitizing drugs and chemicals are crucial.

A Case Study of Photosensitivity Associated with Anaplasma spp. Infection in Cattle.

Anaplasma infection has not previously been reported as a cause of photosensitization. This case presents a five-year-old Holstein cow in her fifth month of gestation with skin injury of nonpigmented areas clearly delimited from adjacent unaffected pigmented skin. Specific lesions included alopecia, localized oedema, desquamation erythema, serous exudation, thick detached skin, fissures, crusting, and necrosis, indicating photodermatitis. Hematological abnormalities were leukocytosis with neutrophilia and normocytic hypochromic anemia. Based on a hemoparasitic examination of blood smears, the organism Anaplasma spp. was observed within the red blood cells. Biochemical analyses revealed increased serum liver enzyme activity associated with hepatocellular damage and cholestasis. This cow was RT-PCR positive for Anaplasma spp. infection. After treatment with oxytetracycline started, its condition improved within 24 h, and it recovered completely within 30 days. In this case, the underlying pathogenic mechanism of Anaplasma spp. infection facilitated the impairment of bile flow and liver function, resulting in hepatogenous photosensitization.

Primary Photosensitization by Chamaecrista serpens in Santa Inês Sheep.

This study aimed to clarify the type of photosensitization induced by C. serpens and to verify if the plant remains toxic after being collected and stored. Eight crossbred sheep, aged between 6 and 36 months, were divided into three groups (G1 to G3). Over 30 days, daily, G1 received an exclusive diet of C. serpens, and G2 and G3 received 10 g/kg/BW and 20 g/kg/BW, respectively. Two other sheep were used as controls (CG). Before administration, the plant had been harvested every 15 days. Liver biopsies and blood samples were taken from all sheep on day zero and weekly. All sheep that received the plant developed clinical signs of photosensitization, and no changes were observed in the serum activities of AST and GGT. On day 30, all sheep except Ov1 from G1 and Ov7 were euthanized and necropsied. All sheep that received the plant developed clinical signs. Macroscopic or histologic lesions were not observed in the liver. Ov 1 recovered 13 days after the end of ingestion. These results demonstrated that C. serpens causes primary photosensitization. It is advisable to avoid grazing on pastures invaded by the plant or to remove them from the pastures immediately after observing the first signs.

The role of TRPV4 channels in cutaneous epithelia.

Transient receptor potential vanilloid 4 (TRPV4) channels are multi-modally activated cation permeable channels that are expressed most organ tissues including the skin. TRPV4 is highly expressed in the skin and functions in skin resident cells such as epidermal keratinocytes, melanocytes, immune mast cells and macrophages, and cutaneous neurons. TRPV4 plays many crucial roles in skin homeostasis to affect an extensive range of processes such as temperature sensation, osmo-sensation, hair growth, cell apoptosis, skin barrier integrity, differentiation, nociception and itch. Since TRPV4 functions in a plenitude of pathological states, TRPV4 can become a versatile therapeutic target for diseases such as chronic pain, itch and skin cancer.

Assessing the frequency of adverse reactions induced by melanin-containing formulations used for the management of solar dermatitis.

BACKGROUND: Melanin from different sources is widely used by many manufacturers to produce cosmetics and sunscreens. Research data show a wide spectrum of biological activities of melanin including the protection against UV radiation and oxidants. According to the research evidence, the topical use of melanin is more effective against inflammation than the hydrocortisone. The most common side effects of topical melanin ointment are local itching, burning, and moderate hyperemia. AIM OF THE STUDY: The purpose of this work is to describe the adverse outcomes of melanin-containing formulas in patients with solar dermatitis, and to compare the frequency of adverse reactions with data from different research reports. METHODS: A Pharmacovigilance questionnaire was developed to assess potential adverse events attributable to the use of melanin ointment. We used a modified survey tool created by Jaber and coauthors. This survey of melanin application documents validated reports of adverse events manifested by objective skin changes. MEDLINE (Ovid); MEDLINE In-Process Citations & Daily Update (Ovid); PubMed (NLM) (Internet); Embase (Ovid); and Cochrane Database of Systematic Reviews were searched for the evidence on adverse reactions of topical melanin application. RESULTS: The responses documented in this survey show reliability and safety of melanin formula used for the photoprotection and treatment of solar dermatitis. Most symptoms encountered in those using melanin were consistent with exposure to excessive amount (more than 4 times per day) of the compound applied topically. Of the total 534 survey responses received, 74% reported no adverse events. A total of 140 completed adverse event reports. Melanin ointment was being administered for the indications of photo injury (burns) in 75%, photodermatitis in 18%, and solar eczematous dermatitis in 7% of patients. Data were compared with rates from other reports. CONCLUSION: We have no evidence that the chemical structure of melanin varies with currently available products, used locally or in other countries, nor that any such variability played any role in the events reported here. Further studies are required to compare the adverse events of topical melanin formulas containing melanins of different origin.

Clearance of Chronic Actinic Dermatitis With Dupilumab Therapy in Chinese Patients: A Case Series.

Chronic actinic dermatitis (CAD) is a rare chronic immunological photo-dermatosis resulting in pruritic eczematous eruption on sun-exposed skin to ultraviolet (UV) light. The disease mechanism may include a delay-type hypersensitivity reaction to an endogenous photo-induced antigen, postulated to be UVR-altered DNA, but the exact pathophysiology is unknown. Minimum erythema dosing and patch testing are diagnostic tools of CAD. There are limited safe and effective treatment options for CAD. Herein, a case series of three patients with severe recalcitrant CAD is presented after being treated with dupilumab off-label. The patients in this study had persistent severe disease and taken the first-line management plan, which consists of topical calcineurin inhibitors (TCI), topical corticosteroids (TCS), and strict photoprotection. However, the above treatment options were not able to control the symptoms. The patients were treated with dupilumab 600 mg first dose, 300 mg biweekly subcutaneously (SC), and hydroxychloroquine. Dupilumab showed excellent clinical benefits, including safe and well-tolerated in chronic actinic dermatitis. Further studies are required to be carried out before being applied in clinical practice.

Use of hydroxychloroquine in dermatology: A multicenter retrospective study in Korea.

Despite the expanding clinical application of hydroxychloroquine in dermatology, the overall data on hydroxychloroquine use among dermatologists are limited. With retrospective review of the medical records of the 790 patients who were prescribed hydroxychloroquine, we classified the diagnoses into 12 disease categories, the lupus erythematosus group being the largest. The lupus erythematosus group had the longest prescription duration (median, 6.2 months), whereas the photodermatitis group had a significantly shorter prescription duration (median, 0.5 months). The overall good response rate was 77.1%. The photodermatitis group had the best response (88.7%), followed by the lupus panniculitis (85.1%) and lichen planus (84.4%). In conclusion, hydroxychloroquine has proven utility for various inflammatory skin diseases, including but not limited to cutaneous lupus erythematosus.

Visible light. Part I: Properties and cutaneous effects of visible light.

Approximately 50% of the sunlight reaching the Earth's surface is visible light (400-700 nm). Other sources of visible light include lasers, light-emitting diodes, and flash lamps. Photons from visible light are absorbed by photoreceptive chromophores (e.g., melanin, heme, and opsins), altering skin function by activating and imparting energy to chromophores. Additionally, visible light can penetrate the full thickness of the skin and induce pigmentation and erythema. Clinically, lasers and light devices are used to treat skin conditions by utilizing specific wavelengths and treatment parameters. Red and blue light from light-emitting diodes and intense pulsed light have been studied as antimicrobial and anti-inflammatory treatments for acne. Pulsed dye lasers are used to treat vascular lesions in adults and infants. Further research is necessary to determine the functional significance of visible light on skin health without confounding the influence of ultraviolet and infrared wavelengths.

Hepatogenous photosensitization in ruminants and horses caused by the ingestion of Chamaecrista serpens in Brazil.

This study aimed to describe the first reports of outbreaks of hepatogenous photosensitization in cattle, sheep, and horses caused by spontaneous ingestion of Chamaecrista serpens, as well as to reproduce poisoning in sheep experimentally. Eleven photodermatitis outbreaks of unknown cause occurred in cattle, sheep and horses on nine farms in the semiarid region of Bahia, northeastern Brazil, between July 2017 and July 2020. Cutaneous lesions of photosensitization initiated until one week after the animals were introduced in paddocks invaded by the plant at the beginning of the rainy season. The photosensitive skin lesions were progressive and consisted of hyperemia, edema, ulcerative-crusted lesions with necrosis, especially in non-pigmented skin areas. The lesions in young animals were more severe. The animals avoided the sun and exhibited hyporexia, weight loss, restlessness, irritability, and severe itching. An experimental study was made using seven sheep, and resulted in photodermatitis, similar to that observed in the natural poisoning, seven days after the beginning of plant ingestion. Two sheep were reserved for the control group. Serum biochemistry changes indicated liver injury caused by the plant. Skin biopsies and liver biopsy guided by ultrasound were performed. The one sheep that had more pronounced skin lesions was euthanized and necropsied. At the necropsy, the liver was enlarged, diffusely pale, and firm, with an evident lobular pattern and an empty gallbladder. Histopathology revealed similar skin and liver lesions in samples from biopsies and the necropsy. There was a marked disorganization of the cords of hepatocytes associated with degenerative necrotic changes on the liver. The cutaneous injuries included orthokeratotic hyperkeratosis, hypergranulosis, acanthosis, and extensive areas of epidermic necrosis and ulceration. Three sheep were protected from sunlight and the lesions regressed within 45 days after the plant's consumption ceased. In conclusion, C. serpens causes hepatogenous photosensitization in ruminants and horses, and should be included in the list of differential diagnoses in cases of photosensitive dermatitis.

Protodioscin levels in Brachiaria spp. in a sheep production system and a brief review of the literature of Brachiaria spp. poisoning in ruminants / Níveis de protodioscina em Brachiaria spp. em um sistema de produção de ovinos e uma breve revisão da literatura da intoxicação por Brachiaria spp. em ruminantes

Plants of the genus Brachiaria, used in several countries as forage, are poisonous to some livestock species. Their toxic principle is protodioscin, and the main form of clinical presentation of the toxicosis is hepatogenous photosensitization. Here we compare protodioscin levels in B. decumbens and B. brizantha and review the literature on the concentrations and methodologies of collection and analysis of the toxic principle in Brachiaria spp. and the risk of contamination of pastures by more toxic species that may facilitate poisoning by plants of this genus in sheep. The experiment was conducted in pastures originally formed by B. brizantha, with many B. decumbens invasion points. The occurrence of cases of poisoning by Brachiaria spp. was the criterion for confirming pasture toxicity. The forage samples were collected at ten random points every 28 days through manual grazing simulation. The samples were analyzed for protodioscin by high-performance liquid chromatography (HPLC) with light scattering by evaporation (ELSD) after being dried and crushed. In the flock of 69 sheep, five poisoning cases occurred, three sheep died, and two recovered. The protodioscin levels found in the evaluated pastures ranged from 0.70 to 0.45%; higher levels appeared in B. decumbens (7.09%) compared to 1.04% in B. brizantha. We suggest that Brachiaria spp. should be avoided in pastures where sheep are grazing.(AU)

Plantas do gênero Brachiaria, utilizadas em vários países como forragem, são tóxicas para várias espécies pecuárias. Seu princípio tóxico é a protodioscina, e a principal forma de apresentação clínica da toxicose é a fotossensibilização hepatógena. Este estudo teve como objetivo comparar os níveis de protodioscina em B. decumbens e B. brizantha e revisar a literatura sobre as concentrações e metodologias de coleta e análise do princípio tóxico em Brachiaria spp. e o risco de contaminação das pastagens por espécies mais tóxicas que podem facilitar a intoxicação por plantas desse gênero em ovinos. O experimento foi conduzido em pastagens originalmente formadas por B. brizantha, com diversos pontos de invasão por B. decumbens. Ocorrência de casos de intoxicação por Brachiaria spp. foi o critério para confirmação da toxicidade da pastagem. As amostras de forragem foram coletadas a cada 28 dias em dez pontos aleatórios por meio de simulação de pastejo manual. As amostras foram analisadas para protodioscina por cromatografia líquida de alta eficiência (HPLC) com dispersão de luz por evaporação (ELSD) após serem secadas e trituradas. No rebanho de 69 ovelhas, cinco desenvolveram a intoxicação, três morreram e duas se recuperaram. Os níveis de protodioscina encontrados nas pastagens avaliadas variaram de 0,70 a 0,45%; níveis mais elevados apareceram em B. decumbens (7,09%) em comparação com 1,04% em B. brizantha. Sugerimos que Brachiaria spp. deve ser evitada no pasto de ovelhas em pastejo.(AU)

Protodioscin levels in Brachiaria spp. in a sheep production system and a brief review of the literature of Brachiaria spp. poisoning in ruminants

ABSTRACT: Plants of the genus Brachiaria, used in several countries as forage, are poisonous to some livestock species. Their toxic principle is protodioscin, and the main form of clinical presentation of the toxicosis is hepatogenous photosensitization. Here we compare protodioscin levels in B. decumbens and B. brizantha and review the literature on the concentrations and methodologies of collection and analysis of the toxic principle in Brachiaria spp. and the risk of contamination of pastures by more toxic species that may facilitate poisoning by plants of this genus in sheep. The experiment was conducted in pastures originally formed by B. brizantha, with many B. decumbens invasion points. The occurrence of cases of poisoning by Brachiaria spp. was the criterion for confirming pasture toxicity. The forage samples were collected at ten random points every 28 days through manual grazing simulation. The samples were analyzed for protodioscin by high-performance liquid chromatography (HPLC) with light scattering by evaporation (ELSD) after being dried and crushed. In the flock of 69 sheep, five poisoning cases occurred, three sheep died, and two recovered. The protodioscin levels found in the evaluated pastures ranged from 0.70 to 0.45%; higher levels appeared in B. decumbens (7.09%) compared to 1.04% in B. brizantha. We suggest that Brachiaria spp. should be avoided in pastures where sheep are grazing.

RESUMO: Plantas do gênero Brachiaria, utilizadas em vários países como forragem, são tóxicas para várias espécies pecuárias. Seu princípio tóxico é a protodioscina, e a principal forma de apresentação clínica da toxicose é a fotossensibilização hepatógena. Este estudo teve como objetivo comparar os níveis de protodioscina em B. decumbens e B. brizantha e revisar a literatura sobre as concentrações e metodologias de coleta e análise do princípio tóxico em Brachiaria spp. e o risco de contaminação das pastagens por espécies mais tóxicas que podem facilitar a intoxicação por plantas desse gênero em ovinos. O experimento foi conduzido em pastagens originalmente formadas por B. brizantha, com diversos pontos de invasão por B. decumbens. Ocorrência de casos de intoxicação por Brachiaria spp. foi o critério para confirmação da toxicidade da pastagem. As amostras de forragem foram coletadas a cada 28 dias em dez pontos aleatórios por meio de simulação de pastejo manual. As amostras foram analisadas para protodioscina por cromatografia líquida de alta eficiência (HPLC) com dispersão de luz por evaporação (ELSD) após serem secadas e trituradas. No rebanho de 69 ovelhas, cinco desenvolveram a intoxicação, três morreram e duas se recuperaram. Os níveis de protodioscina encontrados nas pastagens avaliadas variaram de 0,70 a 0,45%; níveis mais elevados apareceram em B. decumbens (7,09%) em comparação com 1,04% em B. brizantha. Sugerimos que Brachiaria spp. deve ser evitada no pasto de ovelhas em pastejo.

Spontaneous and experimental poisoning by Froelichia humboldtiana in cattle / Intoxicação espontânea e experimental por Froelichia humboldtiana em bovinos

The aim of this work was to describe the epidemiological, clinical and pathological aspects of two outbreaks of spontaneous poisoning caused by Froelichia humboldtiana in cattle in Pernambuco, northeastern Brazil and reproduce experimentally this poisoning in cattle. Spontaneous poisonings of primary photosensitization occurred in two farms at the municipalities of Cachoeirinha and São Caetano and affected twenty-two adult bovines and two suckling calves after the rainy season. All bovines have recovered 21 days after they were removed from the pasture. To reproduce experimental poisoning, three cows and a calf were maintained in a pasture with 1ha composed by F. humboldtiana during 14 days. Clinical signs and skin lesions were similar in both spontaneous and experimental poisoning and consisted of cutaneous itching and hyperemia of non-pigmented areas of skin that evolved into edema, exudative dermatitis and extensive areas of skin necrosis. Serum levels of aspartate aminotransferase (AST), gamma glutamyltransferase (GGT), total, direct and indirect bilirubin were normal in all cattle examined. Histologically, lesions consisted of epidermal necrosis, hyperkeratosis with large amounts of degenerate neutrophils and acanthosis. In the dermis, edema and inflammatory infiltrate composed of eosinophils, lymphocytes and plasma cells mainly around the blood vessels were observed. In the experimental group, clinical signs of photosensitization were observed after the third day of F. humboldtiana consumption. The suckling calf displayed mild clinical signs of photodermatitis on the 8th day of the experiment. It was estimated that the average consumption of F. humboldtiana necessary to initiate clinical signs in each adult bovine was 78kg.(AU)

Os objetivos deste trabalho foram descrever os aspectos epidemiológicos, clínicos e patológicos de dois surtos de intoxicação por Froelichia humboldtiana em bovinos em Pernambuco e reproduzir experimentalmente essa intoxicação em bovinos. Intoxicações espontâneas foram observadas após o início do período chuvoso nos municípios de Cachoerinha e São Caetano. Vinte e dois bovinos apresentaram sinais clínicos e lesões cutâneas compatíveis com fotossensibilização primária, dentre os quais, dois bezerros lactentes. Todos os bovinos se recuperaram totalmente cerca de 21 dias após serem retirados da pastagem. Para reproduzir experimentalmente a intoxicação, três vacas, uma delas com bezerro ao pé, foram mantidas em um piquete de 1ha composto por F. humboldtiana por 14 dias consecutivos. O quadro clínico e as lesões tegumentares, tanto nos bovinos intoxicados nos surtos espontâneos, quanto nos bovinos do experimento consistiram em prurido e hiperemia em áreas despigmentadas de pele, que evoluíam para edema, dermatite exsudativa e necrose de áreas extensas de pele. Em todos os bovinos examinados, os níveis séricos de aspartato aminotransferase (AST), gamaglutamiltransferase (GGT), bilirrubina total, direta e indireta estavam normais. Histologicamente, as lesões consistiram em necrose da epiderme, hiperqueratose com grande quantidade de neutrófilos degenerados e acantose. Na derme havia edema e infiltrado inflamatório composto por eosinófilos, linfócitos e plasmócitos principalmente ao redor dos vasos sanguíneos. Nos bovinos do experimento, sinais clínicos de fotossensibilização foram observados após o terceiro dia de consumo de F. humboldtiana. O bezerro lactente apresentou sinais clínicos leves de fotodermatite no 8º dia do experimento. Estimou-se que o consumo médio de matéria seca de F. humboldtiana necessário para iniciar os sinais clínicos em cada bovino adulto foi de 78kg.(AU)

Protective effect of a topical sunscreen formulation fortified with melatonin against UV-induced photodermatitis: an immunomodulatory effect via NF-κB suppression.

Objective: Melatonin and pumpkin seed oil, along with US FDA approved UV filters were incorporated into a formulation for enhancement of UV protection by exerting an antioxidant effect. The objective of this study was to assess the protective effect of this formulation against ultraviolet (UV) radiation-induced photo dermatitis in rats, which is an established model to study the aetiopathogenic mechanisms in psoriasis vulgaris, as the former exhibits the same features to those of clinical psoriasis vulgaris in humans. Materials and methods: The animals were segregated into five groups (6/group) and all received their respective formulations dermally prior to chronic UV irradiation for 28 days. The test, placebo, and standard groups; received the test, placebo, and standard formulations respectively; whereas the positive control group received only UV radiation. A normal control group was also maintained. Disease and treatment status were analyzed using various techniques by euthanizing the rats after 28 days. Results: The test formulation was able to ameliorate the UV-induced increase in skin fold, epidermal thickness, and skin edema; inhibit the reduction of hydroxyproline content and incidence of LPO within the skin tissues of exposed animals. The formulation was also able to inhibit the release of proinflammatory cytokines; IFN-γ, IL-1ß, IL-6, and TNF-α; and upregulation of NF-κB and COX-2 genes caused by chronic UV exposure. Conclusion: It can be stated that melatonin included in the newly formulated sunscreen was able to inhibit the induction of photodermatitis via immunoregulation of inflammatory cytokines along with NF-κB and COX-2 genes.

Surtos de fotossensibilização e dermatite alérgica em ruminantes e equídeos no Nordeste do Brasil / Outbreaks of photosensitization and allergic dermatitis in ruminants and equidae in northeastern Brazil

O presente estudo foi conduzido com o objetivo de determinar as causas de fotossensibilização em ruminantes e equídeos no Nordeste do Brasil, através da revisão dos laudos de exames arquivados no Laboratório de Patologia Veterinária da Universidade Federal da Paraíba. Durante os quatro anos do estudo foram diagnosticados 22 surtos de fotossensibilização, incluindo 11 surtos de fotossensibilização primária e oito surtos de fotossensibilização hepatógena. A intoxicação por Froelichia humboldtiana foi a principal causa de fotossensibilização e a única causa de fotossensibilização primária. As espécies mais gravemente afetadas por fotossensibilização primária foram os asininos, caprinos, bovinos e ovinos, mas os equinos e mulas também são afetados. A intoxicação por Brachiaria decumbens foi a principal causa de fotossensibilização hepatógena e afetou apenas os ovinos e bovinos. Outras plantas associadas com fotossensibilização hepatógena incluíram Enterolobium contortisiliquum e Lantana camara. Dermatite alérgica foi diagnosticada em dois rebanhos ovinos e em um cavalo. Os animais tinham lesões crônicas, caracterizadas por alopecia, crostas e hiperpigmentação no topo da cabeça, ao redor dos olhos (ovinos) e nos membros (equino). O prurido foi o principal sinal clínico observado nos casos de fotossensibilização primária e hipersensibilidade à picada de insetos.(AU)

The study was conducted to determine the causes of photosensitization in ruminants and equidae in northeastern Brazil through a review of the files at the Laboratório de Patologia Veterinária of Universidade Federal da Paraíba. During four years of the study 22 outbreaks of photosensitization were diagnosed, including 11 outbreaks of primary photosensitization and eight outbreaks of hepatogenous photosensitization. Poisoning by Froelichia humboldtiana was the main cause of photosensitization, and the only cause of primary photosensitization. The most severely affected animals by primary photosensitization are donkeys, goats, cattle and sheep, but horses and mules may also be affected. Poisoning by Brachiaria decumbens was the main cause of hepatogenous photosensitization, and affected only sheep and cattle. Other plants associated with hepatogenous photosensitization in cattle include Enterolobium contortisiliquum and Lantana camara. Allergic dermatitis was diagnosed in two flocks of sheep and in a horse. The animals had chronic lesions characterized by areas of alopecia, crusts and hyperpigmentation on the head, around the eyes (sheep) and at the legs (horse). Itching was the main clinical sign in cases of primary photosensitization and insect hypersensitivity.(AU)