Summer is here! Recently, a friend e-mailed a picture of her infant son to me (and several other physician friends) asking "Is this sunburn or heat rash?" As it turns out, it was urticaria; however, it reminded me what a common question this is from families as the temperatures rise.
The first point is that much of what a parent may be worried is heat rash is not, so a good exam and accurate diagnosis is important. Just as my friend’s son had urticaria, there are other skin conditions that should be considered in the differential diagnosis including sunburn, eczema, erythema toxicum neonatorum, infantile acne, and many others. There are actually three different kinds of "heat rash," or miliaria, which is thought to be caused by an obstruction of the eccrine sweat ducts and brought on by warm temperatures. Miliaria crystallina is the most superficial type of heat rash, with small, thin, fragile vesicles occurring mostly on the head, neck, and trunk; no underlying inflammation is seen. This form is typically seen in young newborns and is not itchy. Miliaria rubra is the form most of us probably think of when we think of "heat rash," manifesting as a local inflammatory reaction with small groups of itchy, erythematous papules and sometimes pustules (which is then called miliaria pustulosa). This form is also more commonly seen in younger infants. Miliaria profunda is less common, most often occurs in individuals who have had repeated episodes of miliaria rubra, and presents as flesh colored papules or pustules. These individuals may show signs of, or be at greater risk for, heat exhaustion because their ability to sweat is impaired.
"The first and most important treatment in most cases is reassurance that this is not a serious condition and will generally resolve on its own once the child is moved to a cooler environment."
In general, treatment for miliaria is conservative and focused on helping to relieve any immediate symptoms. The exception to this is of course patients with miliaria profunda – who should be monitored for signs of heat exhaustion, and patients with signs or symptoms of superinfected skin lesions. That being said, the first and most important treatment in most cases is reassurance that this is not a serious condition and will generally resolve on its own once the child is moved to a cooler environment. Sometimes changing into lighter, looser clothing, using cool compresses, or giving a cool bath (but not ice cold) also can be helpful. If a patient has miliaria rubra and seems to be very itchy and uncomfortable, that can be managed topically with calamine lotion, lanolin, or topical corticosteroids if needed. Occasionally, an oral antihistamine may be needed for cases of more severe itching, although usually symptoms can be managed with topical treatments only. For patients with recurrent miliaria, applying anhydrous lanolin before exercising or going into the heat can help prevent further occurrences.
Anytime you see a patient with true heat rash, or anything the parent is worried may be heat rash, it is a great opportunity to discuss sun/heat safety. Reminders about staying out of the sun at peak hours, wearing sunscreen and hats, keeping hydrated, and knowing the signs and symptoms of heat illness are timely – although, of course, also be mindful and sensitive to the fact that a parent may be feeling worried that they did something "wrong" or irresponsible that brought on her child’s skin condition. On the flip side, I also sometimes have families tell me with the best intentions that "I’m just not ever going to take them outside now," so reassurance that it is good for kids to be outside experiencing the world around them (albeit safely!) is also a good reminder.
Overall, with reassurance and good advice, heat rash is a generally a benign and time-limited condition, and families should be able to quickly return to enjoying their fun summer activities.
Dr. Beers is assistant professor of pediatrics at Children’s National Medical Center and the George Washington University Medical Center, Washington. She is chair of the American Academy of Pediatrics Committee on Residency Scholarships and president of the District of Columbia chapter of the American Academy of Pediatrics. She said she had no relevant financial disclosures. E-mail Dr. Beers at email@example.com.