As outdoor temperatures climb, children and adults may break out in rashes. These skin conditions often get lumped into the catchphrase “heat rash,” but heat is usually an indirect or unrelated factor. Let’s take a look at some examples.
Flushed Skin and Cheeks
One incredible thing about our skin is that it acts as a radiator, cooling the inside of our body when it is hot outside. It does this by relaxing smooth muscle inside blood vessels, which makes the internal diameter larger. As the blood vessel dilates, it carries more blood to the skin. This may show up as flushing of the skin and cheeks. Heat is transferred from the blood to the surface of the skin. The heat then transfers to sweat, which leaves the body through evaporation. When skin and cheeks get flushed in the heat, it is time to seek shade and drink plenty of water!
This might be the most common cause of “heat rash.” Many chemicals touch our skin in the summer months. Sunscreens and insect repellant are rubbed on the skin intentionally, and while their active ingredient is seldom a cause for concern, other chemicals in a particular brand (such as dyes and perfumes) may result in a rash called contact dermatitis. Trace detergents and fabric softeners in clothes, bedsheets and pillowcases may result in a similar rash as our sweat dissolves these chemicals and brings them into contact with our skin.
Insects can be sneaky and bite your skin when you aren’t paying attention. Just ask the kid who plays outside at dusk and wakes up in the morning with lots of itchy bumps on the arms and legs. These sometimes get blamed on the heat, but mosquitos, flies and ants are the real culprit.
Poison ivy rashes occur when a plant oil from poison ivy, oak or sumac permanently binds to the skin. Yes, that’s right… it binds to the skin permanently! If you are allergic to this oil (and many people are) a very itchy rash occurs. This long-lasting rash clears up when the oil-bound skin finally flakes off and is replaced by new skin. Thankfully, your doctor can suggest or prescribe medications to quiet the inflammation and relieve the itch while you wait for the skin to heal.
Will the Real Heat Rash Please Stand Up?
Okay, if these things aren’t really “heat rash,” then what is? The medical definition of heat rash (also known as prickly heat) involves the skin producing sweat, which is unable to leave through a blocked pore. It gets trapped in the skin and causes a red, itchy bump. While this is common in babies, it occurs less often in older children and adults. The treatment for heat rash is removing whatever is blocking the pores and finding a cool, shady spot. Common causes include tight-fitting clothes and baby lotions or oils.
As you can see, there are many causes of skin rash when temperatures heat up, and each type of rash is treated differently. If a rash is bothering you or your child during the summer months, it’s best to see your medical provider to get the right diagnosis and treatment for your particular type of “heat rash.”
Dr Mike Patrick is an Assistant Professor of Pediatrics at the Ohio State University College of Medicine and Medical Director of Interactive Media for Nationwide Children's Hospital. Since 2006, he has hosted the award-winning PediaCast, a pediatric podcast for parents. Dr Mike also produces a national podcast for healthcare providers—PediaCast CME, which explores general pediatric and faculty development topics and offers free AMA PRA Category 1 Credit™ to listeners.
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