What is heat rash?

If you live in a hot and humid climate or have vacationed in one, you know that you can sweat a lot. Sweating is the body’s mechanism for cooling down — as sweat leaves the pores in the skin, it evaporates, taking body heat with it.
If your skin’s ducts become clogged, sweat can’t make it to the surface to evaporate. It becomes trapped and causes irritation. This is known as a heat rash or prickly heat.
If you’re in a warm climate or plan to go to one, it’s essential to know what causes heat rash so that you can prevent it. Equally important are the signs of heat rash so that you can treat it or see the doctor and help them diagnose it to get proper treatment.
There are four prickly heat types, which are classified by how deep the pore blockage is:
- Miliaria crystallina
- Miliaria rubra
- Miliaria pustulosa
- Miliaria profunda
Miliaria crystallina is the mildest and most common form of heat rash. It occurs when pores become clogged on the top layer of skin. Miliaria rubra is the form of heat rash that causes the prickling sensation known as prickly heat.
If Miliaria rubra becomes infected or the tissue becomes inflamed, the bumps tend to fill with pus. This is known as miliaria pustulosa.
If your pores are clogged deep enough to affect the dermis, lesions can form that closely resemble goosebumps. If this is your condition's cause, you have miliaria profunda, the least common form of heat rash.
Main symptoms
Heat rash commonly shows up as a red rash in the affected area. Not everyone experiences the same heat rash symptoms. It may also present as:
Main causes
Your skin has three types of glands that secrete sweat — the eccrine, apocrine, and apoeccrine glands. Of these three, eccrine glands produce the most sweat. Your pores can become clogged for a variety of reasons, which keeps the sweat from flowing correctly.
The pores become blocked because of:
- Keratin plugs in pores
- Excessive sweat over long periods
- Bacteria
- Tight clothing
- Hyperhidrosis
- Medicinal reaction
- Sensitive skin conditions
A keratin plug is a buildup of skin cells that combine with oil secreting through the pores in your skin. These plugs keep sweat from flowing out of the pores and cause irritation. Bacteria can get into your pores through damaged hair follicles and cause infections that can clog your pores and cause heat rash if it is combined with other causes.
Tight clothing can restrict airflow and keep sweat against your skin. Tight clothes trap sweat, which can clog your pores and lead to a heat rash. If you sweat excessively (hyperhidrosis), you are more prone to heat rash — especially if you wear tight clothing or sweat for long periods.
Some medicated patches can cause prickly heat because they stick to or leave residue on the skin.

QUESTION
Ringworm is caused by a fungus. See AnswerDiagnosis for heat rash
If you have a heat rash for a long time, or if it keeps coming back, see your doctor. They will talk to you about your symptoms and conduct a physical exam. This exam will include a close examination of your skin.
Treatments for heat rash
If you experience a heat rash and it goes away after showering and thoroughly drying your skin, you may not need to see a doctor. Home remedies for heat rash often work without a doctor.
Doctors usually treat heat rash with a combination of medication and actions you can take at home to treat it. Home remedies are generally enough to keep the condition from occurring, but if you’re an active and outdoors type, you might need some help.
Medication
In some cases, topical steroids may be necessary to reduce any inflamed tissue that has resulted from the rash. If the itching is severe, your doctor can prescribe calamine lotion to keep it under control and make it more bearable until the rash goes away.
If your heat rash is caused by skin cells collecting in your pores (keratin plugs), your doctor might give you some anhydrous lanolin ointment. This medicinal lotion helps dead skin cells fall off of the skin and keeps the skin hydrated.
Home remedies
Many people can treat prickly heat at home. If you have a rash after being out in the heat and sweating, take a hot shower and use a mild antibacterial soap. Dry thoroughly and put on loose clothing. Prickly heat should subside within a few days. Often, it goes away as soon as you are dry.
If the home remedy doesn’t work, or you keep getting a heat rash, take a picture of the rash for your doctor to see. You might have other skin conditions that are causing your prickly heat and will need to diagnose any conditions further.
Health News
- After Salmonella Cases Double in a Week, Cantaloupe Recall Expanded
- COVID Vaccines Curbed Pandemic-Linked Surge in Preemie Births
- Could a 'Brain Coach' Help Folks at Higher Risk for Alzheimer's?
- Early Promise for Stem Cell Therapy to Curb MS
- Internet Poses No Threat to Mental Health, Major Study Finds
More Health News »
Possible complications and side effects
If your heat rash is recurring, you can’t get rid of it, or you don’t treat it, it can turn into infections within your pores. Infections can lead to more severe conditions, so it’s essential to see your doctor if your heat rash doesn’t go away following the home treatments.
You may develop staph infection, have trouble regulating your body heat, or develop hyperhidrosis in unaffected areas.
Health Solutions From Our Sponsors
DermNet NZ: “Miliaria."
John Hopkins Medicine: "Prickly Heat."
Temperature, Medical Physiology and Beyond: "Physiology of sweat gland function: The roles of sweating and sweat composition in human health."
StatPearls: “Miliaria.”
University of Rochester Medical Center: "Prickly Heat."
Top How Long Does It Take Heat Rash to Go Away Related Articles
Are Hives and Rash the Same Thing?
Learn how to tell the difference between a rash and hives and how to treat both.Heat Rash
Heat rash is a skin irritation caused by excessive sweating. It can occur at any age and it appears as a rash that itches or feels prickly, and looks like a red cluster of pimples or small blisters.Heat rash remedies include OTC creams and sprays. Usually heat rash resolves when the skin is cooled sufficiently. Medical treatment may be necessary if the sweat glands become infected.
Heat Rash: How Do You Get Rid of It?
Do you know what heat rash looks like? Prickly heat is an itchy skin problem. It can cause pus-filled papules (blisters), red bumps, discomfort, and itching skin rashes. Medical care may include anti-itch ointment and keeping the skin cool in an air-conditioned room.How Do I Deal With Pregnancy in the Summer Heat?
When you’re dealing with a summer pregnancy, it’s important to limit activities that raise your core temperature.How Do I Get Rid of Heat Rash on My Face?
What is heat rash on the face and how do you treat it? Learn what medical treatments can help ease heat rash on your face and speed up your recovery from heat rash.How Long Does a Heat Rash Last on a Baby?
Heat rash is a common issue that affects many babies. Learn the signs of heat rash, what causes it, how long it lasts, how doctors diagnose it, and what you can do to treat it.lanolin
Lanolin is an emollient used to soften and soothe dry, scaly skin, skin irritation and itching. Lanolin is used to treat diaper rash in infants, sore or cracked nipples from breastfeeding, chafed skin and minor skin irritations from incontinence, dry and scaly skin, and skin irritation from blisters and minor burns. Common side effects of lanolin include skin irritation and redness, and burning and stinging. Excessive application of lanolin is unlikely to cause any serious effects. Lanolin has no known severe, serious, moderate, or mild interactions with other drugs.pramoxine/calamine topical
Pramoxine/calamine topical is an over-the-counter (OTC) medication used as a lotion or cream for the temporary relief of pain, itching, and discomfort from coming into contact with poison ivy, oak, or sumac. Common side effects of pramoxine/calamine topical include burning or stinging, itching (pruritus), and irritation. Consult your doctor before taking if pregnant or breastfeeding. For external use only.Skin Rash
The word "rash" means an outbreak of red bumps on the body. The way people use this term, "a rash" can refer to many different skin conditions. The most common of these are scaly patches of skin and red, itchy bumps or patches all over the place.Skin Problems: Contagious Rashes, Bumps, and Blisters
Why do rashes, bumps, and blisters appear on your skin? There are several medical causes. Find out what causes bumps, rashes, and other skin conditions in adults and children. Whether on the arm, leg, trunk, or head, itchy or painful rashes and bumps can often be treated using home remedies or medicine.Skin Conditions Below the Waist
Skin conditions like acne, eczema, psoriasis, and allergies may produce redness and other symptoms. See your dermatologist right away if you develop itchy skin, rashes, pimples, or other skin conditions. Dermatology experts are best if you suspect skin cancer or other serious skin disease.What Does a Stress Rash Look Like?
Stress often affects the skin adversely. It causes the formation of a stress hormone that increases oil production in the body, making it prone to acne. Stress may also cause itchy welts to appear on the skin.