Why does the skin itch after sun exposure in summer?

Normally, skin itching caused by sun exposure in summer may be due to factors such as dry skin, sweat irritation, solar dermatitis, cholinergic urticaria, or atopic dermatitis. It is recommended to seek timely medical consultation to identify the underlying cause and receive targeted treatment. Detailed explanations are as follows:

1. Dry Skin

Ultraviolet radiation accelerates evaporation of skin moisture, reducing the water content in the stratum corneum. Once the skin barrier is compromised, external irritants can more easily penetrate and stimulate sensory nerve endings, causing itching. Apply a gentle moisturizing lotion or cream to replenish skin moisture promptly.

2. Sweat Irritation

If sweat is not promptly removed after perspiration, its electrolytes and metabolic waste products can create a hypertonic environment on the skin surface, disrupting the acid-base balance and irritating nerve receptors in the stratum corneum and superficial dermis, causing itching. Cleanse the skin with warm water after sweating to maintain dryness and wear loose, breathable clothing to reduce sweat accumulation.

3. Solar Dermatitis

Ultraviolet radiation prompts skin cells to release inflammatory mediators such as histamine, causing dilation and increased permeability of dermal blood vessels, leading to inflammatory manifestations such as erythema and edema, while simultaneously stimulating nerve endings to produce itching. Well-defined red patches appear on exposed skin areas, and severe cases may develop blisters and exudation. Patients may use calamine lotion, hydrocortisone butyrate cream, or other medications as directed by a physician.

4. Cholinergic Urticaria

An increase in body temperature causes impulses in cholinergic nerves, releasing acetylcholine that acts on skin mast cells, triggering degranulation and release of active substances like histamine, resulting in dilated small blood vessels and increased permeability, causing wheals and itching. A red halo often surrounds the affected area, accompanied by prickling or burning pain. Oral antihistamines such as cetirizine hydrochloride tablets, ketotifen fumarate tablets, or loratadine dispersible tablets may be taken to alleviate symptoms.

5. Atopic Dermatitis

Patients with atopic dermatitis have abnormal skin barrier function. Ultraviolet radiation further damages the skin barrier, activating inflammatory cells and releasing inflammatory factors that exacerbate the skin's inflammatory response, stimulating nerve endings and causing intense itching. Polymorphic rashes such as erythema, papules, exudation, and crusting may also appear. Under a doctor's guidance, patients can apply topical medications such as hydrocortisone cream, tacrolimus ointment, or pimecrolimus cream for treatment.

Maintain good lifestyle habits in daily life and avoid consuming spicy or irritating foods such as pepper, chili, and garlic, which may hinder recovery.