Miliaria, commonly called a heat rash or prickly heat, develops when sweat is trapped underneath your skin, blocking your pores. Pimples, also called acne, develop when the hair follicles located under the skin become blocked. Although a heat rash and pimples both occur because of pore blockage, there are many differences between the two skin conditions.
A heat rash typically occurs in hot weather or when the body sweats profusely, such as during an exercise workout. The rash may also develop during cold weather. For example, if you wear too many layers of clothing or sleep under an electric blanket and sweat too much, your pores may become clogged.
Many myths exist about what causes pimples, such as eating greasy foods or chocolate, having dirty skin or stress. Although the exact cause of pimples isn’t known, hormonal changes do play a role, according to the U.S. National Library of Medicine. Hormonal changes typically affect pregnant women and young adults in their teenage years. Pimples, however, may develop regardless of your age.
Types and Symptoms
The types of pimples vary according to the symptoms. Pustules are bumps that are tender and red and filled with pus. Nodules are solid lumps under the skin. Papules are small raised pimples. They are usually tender or red because of a hair follicle infection or inflammation. Cysts appear as boils or lumps underneath the skin, filled with pus. Pimples open at the surface of the skin are called blackhead comedones. Whitehead comedones are raised, closed bumps that are the same color as your skin.
There are three types of heat rash. Miliaria profunda resembles goose bumps, states the Mayo Clinic. Signs of the heat rash appear after working out. A heat rash called miliaria crystalline is clear, tiny bumps that appear on the surface of the skin. Miliaria rubra are red, itchy bumps that develop on the outer layer of your epidermis.
Pimples commonly appear on your face. The pimples, however, can also appear on your back, chest, shoulders and neck. A heat rash also appears on your beck, chest and shoulders. The rash also appears under your armpits, in the creases of your elbows and your groin. If you’re a female, a heat rash may appear under your breasts.
A mild case of heat rash typically disappears by itself in approximately 10 days, but you must keep your skin dry and cool. More severe cases may require topical medication such as anhydrous lanolin. Treatment for pimples depends on the severity and recurrence. For example, there are over-the-counter (OTC) and prescription topical treatments, antibiotics and isotretinoin. OTC treatments can take up to eight weeks before pimples disappear. Prescription topical treatments clear up pimples in about four to eight weeks, according to the Mayo Clinic.