Level 1: What is prickly heat? Prickly heat is a common skin problem, especially in summer. It usually appears as small red dots or blisters on the skin. Heat rash usually occurs in areas with clogged pockets of sweat glands, which secrete sweat to regulate body temperature. When these sweat glands become clogged, sweat cannot drain properly, causing inflammation and tingling. Level 2: What are the causes of prickly heat? 1. High temperature and high humidity environment: High temperatures and high humidity in summer can easily lead to increased sweating in the human body, leading to prickly heat. 2. Skin friction: Wearing clothes that are too tight, too thick or airtight can easily cause friction.