The spring breeze is warming, and the season of high incidence of ultraviolet allergies has also arrived. Today, dermatology takes you through a few common UV allergic dermatitis.
Ultraviolet rays are divided into short-wave ultraviolet light (UVC, wavelength 180~280nm), medium-wave ultraviolet light (UVB, wavelength 280~320nm) and long-wave ultraviolet (UVA, wavelength 320~400nm).
(Source: Tencent Medical Code)
1. Solar dermatitis
Solar dermatitis is mainly an acute phototoxic reaction caused by UVB irradiation on the local skin. There are two types of solar dermatitis:
1. Phototoxic reactions: can occur in anyone and are acute inflammatory reactions caused by medium-wave ultraviolet radiation on the skin;
2. Photoallergic reactions: Occur only in a small number of people with allergies. The possible mechanism is that the photoreceptor substance, under the action of light energy, turns the anterior half antigen into a hemiantigen, which binds to skin proteins to form a total antigen and stimulates the body to produce an immune response.
Solar dermatitis mostly occurs in late spring and early summer, and people with light skin color are prone to disease; the skin occurs within a few hours after being exposed to strong sunlight; it tends to occur in the face, neck, arms and other parts exposed to sunlight; it is manifested as local diffuse erythema and edema of the skin, and blisters and bullae can occur in severe cases; the affected area is burning, dry, slightly itchy or tingling; and there can also be systemic symptoms such as fever, nausea, vomiting, and dizziness.
2. Plant solar dermatitis
After eating vegetables containing certain light-sensitive substances, patients who have been exposed to a large amount of sunlight cause acute skin inflammation in light-exposed areas, mainly caused by UVA.
Patients have eaten a large number of light-sensitive vegetables in the days before the onset of the disease, such as amaranth, gray cabbage, etc.; the skin is affected within a few hours after strong sunlight exposure; it is easy to occur in the skin of the exposed area, manifested as local skin diffuse erythema and edema, and the high degree of facial edema makes it difficult for the patient to open his eyes and open his mouth, and in severe cases, blisters, bullae, and blood blisters can occur, and erosion, ulceration and necrosis occur after rupture, and scars can be left after healing.
3. Polymorphic solar rash
Polymorphic solar rash may be a delayed allergic reaction. Pathogenic light is mostly UVA, which can also be caused by both UVA and UVB.
It occurs more often in young women; it occurs within a few hours to 5 days after sun exposure in the spring or early summer, resolves in autumn and winter, and lasts for many years; it feels itchy in the exposed area after sun exposure, followed by erythema, papules, blisters, and other forms of rash, and chronic lesions may appear lichenoid changes with purpura or telangiectasia.
4. Chronic actinic dermatitis
Chronic photochemical dermatitis is a group of diseases characterized by chronic photosensitivity, including persistent photoreaction, photosensitive dermatitis, and photoretic reticuloblastic hyperplasia.
Chronic skin inflammation that occurs at the exposed site can develop to the surrounding non-exposed areas; males and outdoor workers are more common and rarely occur in people under 50 years of age; the rash is a chronic eczema-like change, including erythema and plaque of the skin, bright redness of the skin lesions in acute exacerbations, edema, papules and small blisters, dark redness of the skin lesions in the chronic phase, thickening of the lichen, surface scales, and clear boundaries; histopathological changes to chronic eczema changes, which can also resemble pseudo-lymphoma-like infiltrates.
differential diagnosis
The differential diagnosis of UV allergic diseases should consider contact dermatitis, seborrheic dermatitis, facial eczema, atopic dermatitis, niacin deficiency, pox-like vesicles, follicular mucinosis, leprosy, and cutaneous T-cell lymphoma.
Treatment of ultraviolet allergies
Patients with mild disease can be treated with cold and wet compresses to avoid sunlight exposure, which is generally cured within 2 to 3 days; patients with severe diseases are recommended to seek medical treatment immediately, and the acute erythematous edema skin lesions should be treated with 3% boric acid solution or normal saline cold wet compresses, topical calamine lotion, glucocorticoids, etc., and the system should be treated with antihistamines, vitamin C, vitamin B, etc.; those with severe systemic symptoms need to be hospitalized. Patients with chronic disease may also require systematic use of niacinamide or hydroxychloroquine, systemic low-dose glucocorticoids or triptolides for disease control in acute exacerbations, and in severe cases, gazandamide or immunosuppressants.
Prevention of ultraviolet allergies
1. Avoid sun exposure: 10:00-14:00 is the strongest time for ultraviolet radiation, and you should try to avoid going out; when you must go out, cover with hats and clothes, apply sunscreen;
2. Diet: Eat more foods rich in vitamin E and vitamin C to weaken the body's sensitivity to ultraviolet rays; avoid or reduce the consumption of light-sensitive foods or drugs;
3. Choose skin care products and cosmetics carefully: mainly gentle to avoid skin irritation .