Rash all over the body in adults: causes, types, and solutions

With the arrival of summer and high temperatures, many adults experience uncomfortable skin reactions. Body rashes are one of the most common during warm and humid seasons, mainly appearing on the neck, shoulders, chest, and skin folds. Although this condition also affects newborns, its presentation in adults requires a different understanding of how to identify and treat it properly. In this article, dermatology experts explain everything you need to know about this summer problem.

What causes rashes during heat?

Dr. Angela Lamb, board-certified dermatologist at Mount Sinai in New York, states that the medical term for this condition is “miliaria.” It occurs when sweat glands and their ducts become blocked due to a combination of high temperatures and excessive humidity. When sweat gets trapped under the skin, small bumps or blisters emerge, causing itching and discomfort.

Adults living in warm, humid regions are more prone to developing this condition. Dr. Rajani Katta, a private-practice dermatologist in Houston, comments that up to 30 percent of adults in tropical climates experience some form of this problem. Tight clothing worsens the situation because it prevents the skin from breathing properly and promotes moisture retention.

Three types of miliaria you should recognize

There are three distinct types of this condition, each with its own characteristics. Miliaria crystallina is the mildest form. It is characterized by small sweat droplets trapped under elevated skin, without significant inflammation or redness. It usually does not itch and is more common in newborns, though it can affect adults.

Miliaria rubra is the most common presentation in adults. Dr. Katta describes this variant as “very red, bumpy, and notably itchy.” It occurs when sweat blocks in the middle of the epidermis, a deeper layer of the skin than the previous one. This form causes greater irritation and discomfort.

Finally, miliaria profunda is the least common but most severe variant. It arises when obstructions affect the dermis, the deepest layer of the skin. Although it causes less itching than the rubra type, the resulting bumps are firmer, intensely red, and painful.

These manifestations are often located in the armpits, groin, neck, abdomen, and under the breasts. Adults are particularly susceptible when wearing tight clothing or engaging in activities that cause excessive sweating.

Differentiation from other skin conditions

Body rashes in adults are often confused with other dermatological conditions. Eczema is a common case, especially during summer when extreme weather conditions can trigger outbreaks in predisposed individuals.

Both conditions share features like redness and itching, but have notable differences. Eczema tends to appear more irregular and scaly, with poorly defined edges. In contrast, heat rash appears as clearly delineated bumps.

Another confusing condition is polymorphic light eruption, a rash with burning sensation formed by small inflamed bumps. Unlike heat rash, this condition is triggered solely by prolonged sun exposure, not by temperature or humidity. It is particularly common when people travel to sunny regions during spring or early summer, after months without intense sun exposure.

Immediate and effective treatment

If you develop a full-body rash, the first essential step is to move to a cooler environment, explains Dr. Lamb. Seek shade, avoid peak heat and humidity hours. Remove tight clothing and wash off thick lotions like sunscreens or moisturizers that block natural skin perspiration.

Apply cold showers or warm compresses with a clean cloth to relieve discomfort. Dr. Nadine Kaskas, a board-certified dermatologist at Mount Sinai, recommends over-the-counter ointments like calamine lotion to soothe itching. If irritation persists or worsens, consult your doctor, as a topical steroid cream may be necessary under prescription.

Without specific treatment, the rash usually resolves on its own once you leave the hot, humid environment. However, there is a risk of secondary infection if blisters open and the skin is not kept clean.

Prevention strategies for adults

Prevention is especially important for adults living in hot climates or working outdoors. Dr. Katta emphasizes that this rash is a warning sign: your sweat glands are not functioning optimally, which could potentially increase vulnerability to heat exhaustion or heatstroke.

Take preventive measures when exposed to heat: seek shade, take frequent breaks, avoid strenuous efforts, and stay constantly hydrated. Dr. Lamb recommends carrying portable fans that can be hung around the neck to maintain airflow.

Clothing also plays a key role in prevention. Wear loose, lightweight garments that allow sweat to evaporate from your skin, advises Dr. Katta. Breathable fabrics are essential for your body to regulate temperature naturally. If you notice any skin irritation during heat exposure, take immediate steps to cool down and prevent more serious complications.