With the onset of summer, sun-induced skin reactions are on the rise and most are diagnosed as “solar dermatitis”. In fact, there are many kinds of sun-induced skin diseases, which are easily confused clinically and require strong clinical experience to diagnose.
I. Classification and performance
1.Sunburn
That is, solar dermatitis belongs to one of the acute sun-damaged skin diseases. The English word for solar dermatitis is solardermatitis, which is synonymous with sunburn, and should be translated as “sunburn” in Chinese. The disease is most often seen in the spring and summer months, when the patient has a history of strong sun exposure, such as a vacation to the beach, or the use of tanning beds to increase the tan. The process is acute, with well-defined erythema and edema appearing on the exposed skin 4 to 6 hours after sun exposure. In severe cases, blisters and macules appear. There is a burning sensation and tingling, and it may also be pruritic. The lesions peak in 12 to 24 hours, followed by fine flaking and hyperpigmentation. It can last for several days.
2.Phototoxic dermatitis
This disease is similar to solar dermatitis, but solar dermatitis is caused by excessive sun exposure, while phototoxic dermatitis requires internal use of phototoxic substances or external use of phototoxic drugs in addition to sun exposure, followed by sun exposure or ultraviolet radiation. The lesions occur minutes to hours after exposure to light and are an acute process. The clinical presentation is a severe sunburn-like reaction at the light-exposed area. In cases of skin exposure to phototoxic substances, the lesions are limited to the area of exposure. Long-lasting (up to several months) hyperpigmentation remains after the lesions fade.
Common phototoxic foods include mudskippers, mud snails, certain plants and drugs such as dihydrochlorothiazide. The plants psoralen, 5-methoxypsoralen (bergapten), 8-methoxypsoralen, angelicin, etc., are all furanocoumarins and are important phototoxic substances. Plants rich in these substances include parsley, celery and citrus. Umbelliferae (umbelliferae) plants such as fennel, carrots, anemone, and Rutaceae (rutaceae) plants such as figs, sweet citron, lemon, rue, etc. are also rich in psoralen. Foods that commonly cause this disease include wild greens (e.g. ashwagandha), parsnips, certain herbs such as fresh forebears, peppermint, fresh fungus, etc.
The topical application of psoralen for vitiligo often causes phototoxic dermatitis, in addition to the juice of carrot, fig, sweet citron, lemon, etc. applied to the skin after sun exposure can also cause phototoxic dermatitis.
In addition to the typical manifestations, taking tetracycline, psoralen, chloramphenicol, mercaptopurine, etc. can cause phototoxic nail release, which manifests as light pressure pain and separation of the distal 1/3 nail plate, mostly occurring after 2 weeks of medication.
The disease gradually decreases after the discontinuation of phototoxic substances and can be completely recovered.
3.Light allergic dermatitis
It is eczema-like dermatitis caused by internal use or skin contact with photoallergens and then by sun exposure. Most in the exposure to light allergens and ultraviolet radiation 24 hours after the occurrence of the acute process. The eczema-like lesions appear on the skin in the light-exposed area, with clear borders at first, and can extend to non-exposed areas with repeated occurrences; those caused by external exposure are limited to the contact area. Unlike phototoxic dermatitis, this disease does not leave pigmentation.
Certain drugs, such as quinine and chloroquine, can cause lichen planus-like reactions, mostly in sunny areas, and unlike lichen planus, there is no oral mucosal damage in this disease.
Photoallergic dermatitis can gradually subside after stopping exposure to photoallergens, or it can become persistent dermatitis.
4.Panion Lager
This disease also manifests as erythema, desquamation and hyperpigmentation of the skin in light-exposed areas or areas of friction and heat on the body, a chronic process that can last for months or years. It is often associated with diarrhea or dementia.
The disease is caused by vitamin niacin deficiency and is easily caused by dieters who consume too little animal fat, mainly corn, or drugs such as isoniazid, 6-mercaptopurine, or 5-fluorouracil. Niacin supplementation can quickly relieve symptoms.
5.Polymorphic heliotrope
The disease is most common in women under 30 years of age, and 10% to 50% have a family history or no obvious family history. The symptoms occur in spring and early summer, and the rash can gradually remit in summer and autumn, i.e. sclerosis, and will still recur in the following year. The lesions develop after sun exposure and are acute and intermittent, occurring 30 minutes to a few hours after sustained sun exposure, with further exposure avoided and the lesions fading within 7 days without scarring.
The lesions are of various forms, including papules and papules, plaques, eczema, insect bites, and erythema multiforme, with one type predominating in each patient. The lesions are distributed in sun-exposed areas, and are more common in winter in areas covered by clothing (e.g., anterior neck V area, lateral forearm), often tending to appear in the same area, and the duration of the disease varies from a few months to several years.
6, photochemical itchy rash
The disease has a pre-pubertal onset, is more common in women, 15% to 50% have a family history, and 10% have an atopic body. The lesions are present all year round, aggravated in summer and reduced in winter. Most patients remit in adulthood. The rash is mainly papules and nodules, with intense itching and obvious scratch marks, commonly papules and nodules, with surface epidermal peeling, which may also appear as eczema-like and mossy. The distribution of sun-exposed areas, cheeks, nasal dorsum, auricle, lower lip and upper and lower extremities, unexposed areas are often involved (common on the buttocks), but the lesions are light.
7.Pox-like blistering disease
The disease develops in childhood (mostly starting at the age of 2 to 3 years old), is more common in males, and can naturally resolve by adolescence. It is induced by sunlight exposure in summer and reduces or completely disappears in winter. The lesions occur a few hours after sun exposure and last for several weeks. The rash appears repeatedly in batches and is symmetrically distributed on sun-exposed areas, such as the face and back of the hands.
8.Solar urticaria
The age of onset of this disease is mostly seen from 10 to 50 years old, with an acute course. The rash appears 5 to 10 minutes after sunlight exposure and fades 1 to 2 hours after avoiding sunlight. The lesions appear as erythematous and windy, distributed in sun-exposed areas, repeatedly exposed areas may have increased tolerance, severe patients may be accompanied by headache, nausea, bronchospasm, pallor and syncope.
9.Chronic photodermatitis
Once called chronic photoreactivity and light-like reticulocytosis. Mostly seen in elderly men, manifesting as persistent dermatitis or eczema-like lesions, generally persisting for more than 3 months even after avoiding sun exposure, may be accompanied by infiltrative papules and plaques (characteristic), mainly involving the exposed area or may extend to the covered area, occasionally showing erythrodermic-like manifestations.
II. Treatment and prevention
The key to treatment is avoidance of light and the continued use of phototoxic substances and photoallergens. The lesions can be treated with topical glucocorticoids. Acute and severe lesions can also be treated with short-term systemic application of glucocorticoids.
The key to prevention is also light avoidance. Physical shading is recommended, as is the use of sunscreen.