Sensitivity of the skin to a light source can take various forms. People with particular skin types are more sensitive to sunburn. Particular medications make the skin more sensitive to sunlight; these include most of the tetracycline antibiotics, heart drugs amiodarone, and sulfonamides. Particular conditions lead to increased light sensitivity. Patients with systemic lupus erythematosus experience skin symptoms after sunlight exposure; some types of porphyria are aggravated by sunlight. A rare hereditary condition xeroderma pigmentosum (a defect in DNA repair) is thought to increase the risk of UV-light-exposure-related cancer by increasing photosensitivity.
Apart from vision, human beings have many physiological and psychological responses to light. In rare individuals an atypical response may result in serious discomfort, disease, or injury. Some drugs have a photosensitizing effect. Properties of natural or artificial light that may abnormally affect people include:
Timing of light (upset of normal circadian rhythms, seasonal affective disorder, sleep disorders)
Intensity of light (photophobia, sunburn, skin cancer)
Wavelength of light ( in lupus, urticaria )
Rapid flickers in intensity of light may trigger or aggravate epilepsy or migraine headaches.
Other effects may include vertigo, or chronic fatigue syndrome.
Arthralgia literally means joint pain; it is a symptom of injury, infection, illnesses (in particular arthritis) or an allergic reaction to medication.