Chronic Actinic Dermatitis Revisited.

BACKGROUND: Chronic actinic dermatitis (CAD) is a persistent eczematous photodermatitis classically described in older, white men with contact allergy to plants. However, evidence from recent studies suggests that some demographics of CAD patients may be changing. OBJECTIVE: The aims of the study were to determine the frequency of CAD in patients presenting with photosensitive eruptions and to identify the allergens and photoallergens most closely associated with this condition. METHODS: We identified all patients with a diagnosis of CAD from 246 consecutive records of patients undergoing photopatch testing from July 1994 to June 2018 and summarized the demographics and test results in comparison with non-CAD patients. CONCLUSIONS: Nineteen (7.7%) of the 246 patients evaluated had CAD with a male-to-female ratio of 1:1.7 among CAD patients. Compared with non-CAD patients, photocontact allergy and/or contact allergy to sesquiterpene lactone mix and contact allergy to fragrances were significantly more common in CAD. Contact allergy to p-phenylenediamine was also common. The results of this study suggest that CAD presents in a broader demographic range, including both men and women of both light and dark skin types. Phototesting and photopatch testing should be considered when patients present with clinical findings consistent with CAD.

Transduction of the Geomagnetic Field as Evidenced from alpha-Band Activity in the Human Brain.

Magnetoreception, the perception of the geomagnetic field, is a sensory modality well-established across all major groups of vertebrates and some invertebrates, but its presence in humans has been tested rarely, yielding inconclusive results. We report here a strong, specific human brain response to ecologically-relevant rotations of Earth-strength magnetic fields. Following geomagnetic stimulation, a drop in amplitude of electroencephalography (EEG) alpha-oscillations (8-13 Hz) occurred in a repeatable manner. Termed alpha-event-related desynchronization (alpha-ERD), such a response has been associated previously with sensory and cognitive processing of external stimuli including vision, auditory and somatosensory cues. Alpha-ERD in response to the geomagnetic field was triggered only by horizontal rotations when the static vertical magnetic field was directed downwards, as it is in the Northern Hemisphere; no brain responses were elicited by the same horizontal rotations when the static vertical component was directed upwards. This implicates a biological response tuned to the ecology of the local human population, rather than a generic physical effect. Biophysical tests showed that the neural response was sensitive to static components of the magnetic field. This rules out all forms of electrical induction (including artifacts from the electrodes) which are determined solely on dynamic components of the field. The neural response was also sensitive to the polarity of the magnetic field. This rules out free-radical "quantum compass" mechanisms like the cryptochrome hypothesis, which can detect only axial alignment. Ferromagnetism remains a viable biophysical mechanism for sensory transduction and provides a basis to start the behavioral exploration of human magnetoreception.