Prickly heat is a mild inflammation of the sweat gland area of the skin that occurs when sweat does not evaporate easily due to hot weather and high humidity and impregnates the epidermis, blocking the sweat gland opening along with dirt on the skin. White prickly heat: tiny, clear, very superficial and non-inflammatory reaction blisters. White rash may occur in bedridden patients with increased sweating due to fever or in children whose clothing prevents heat and moisture from escaping, such as those who are wrapped. The rash is asymptomatic, ruptures easily with minor friction, and is thus short-lived.