Skin allergies caused by sun exposure

Introduction Skin irritation caused by sunlight refers to the acute phototoxic reaction of the skin caused by excessive exposure of ultraviolet light in the sun to exposed parts of the skin. The mechanism is that when the skin tissue is irradiated with light, an antigenic substance is formed, which causes the body to be sensitized, resulting in an allergic reaction. Due to the superficial effect of UVB, it is only expressed in the epidermis of the skin. And after strong sunlight, it will quickly cause necrosis of the skin epidermal keratinocytes, and release the medium to cause dermal vasodilation, which causes tissue edema. The melanocytes then accelerate the synthesis of melanin under intense illumination of sunlight, thereby darkening the sun-dried skin.

Cause

Daylight includes ultraviolet light, visible light, and infrared light, of which ultraviolet light damages the human body. The ultraviolet rays are classified into short-wave ultraviolet rays (wavelengths of 180-290 nm), medium-wavelength ultraviolet rays (wavelengths of 290-320 nm), and long-wavelength ultraviolet rays (wavelengths of 320-400 nm). Different wavelengths of purple money lines can be absorbed by different tissues in different layers of the skin. The longer the wavelength, the stronger the penetration. The medium-wave ultraviolet light is mainly absorbed by the epidermis, which damages the epidermis, and the long-wave ultraviolet rays reach the upper part of the dermis and can act on blood vessels and other tissues.

In nature, the absorption and scattering of air, clouds, dust particles, water vapor, etc. in the atmosphere can filter out short-wave ultraviolet rays to protect the human body from harm, while long-wave ultraviolet rays only affect individuals with light perception, so The most harmful to the human body is UVB. The abnormal reactions caused by sunlight on the human body are divided into phototoxicity and allergic reactivity.

an examination

Related inspection

Skin prick test blood routine

A few hours to more than 10 hours after sun exposure, the exposed skin has edema and erythema with clear boundaries. In severe cases, blisters may appear, and the affected area may have a burning or tingling sensation. Symptoms often peak within 24 hours, and erythematous edema subsides after sputum or large desquamation, mild hyperpigmentation. Severe cases may be accompanied by systemic symptoms such as headache, palpitations, nausea, and fever.

Differential diagnosis

1, skin allergies: is a very common form of allergies, 20% of people have skin allergies. Skin allergies are also known as "sensitive" skin. From a medical point of view, skin allergies mainly refer to cosmetics, chemicals, pollen, certain foods, polluted air, etc., which cause skin irritation, such as adverse reactions, resulting in redness, itching, peeling and allergic dermatitis. And other anomalies. Sensitive skin can be said to be an unstable skin, a skin that is always on high alert. Pay special attention to its care.

2. Wind-like damage at the skin line: Use a cotton swab (or pencil tip) to scribe on the patient's back skin, and use force to avoid scratching the skin. 1 to 3 minutes after the stroke, the wind-like lesions consistent with the scratches were found at the scribe line, and the diameter was 3 to 5 mm for 10 to 60 minutes. The patient felt itching, which was the skin scratch.

3, light allergy: refers to ultraviolet radiation (such as sun exposure), the exposed parts of the skin appear red rash, papules or bullous rash, with burning, itching pain. The severity of skin lesions is directly proportional to the intensity, distance and duration of light exposure.

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