What is a rash that effects the upper arms and most of legs bright red HOT goes away in about 20 min appears daily Dermatologist diagnose unless he sees it but randomly?

Suspected condition: Cholinergic urticaria (heat rash)

Characteristics:

- Small, red, itchy bumps that appear on the skin after exposure to heat or sweating

- Typically occur on the upper arms, chest, and back, but can also affect other areas of the body

- Lesions are typically 2-3 mm in diameter and can appear in clusters

- Itching can be intense

- Lesions typically resolve within 30-60 minutes

Diagnosis:

- Cholinergic urticaria is usually diagnosed based on the patient's symptoms and a physical examination of the skin

- A skin biopsy may be performed to confirm the diagnosis

Treatment:

- Treatment for cholinergic urticaria typically involves avoiding triggers (heat and sweating) and using topical or oral antihistamines to relieve itching

- In some cases, oral corticosteroids may be prescribed to reduce inflammation