Red rash due to hot weather

The most common cause of rashes in hot weather is prickly heat. The appearance of rashes is basically similar, and it is difficult to make an accurate judgment based solely on the appearance. Even prickly heat has many different types. The biggest characteristic of prickly heat is that it tends to appear in wrinkled parts of the body, increases significantly after sweating, and has no symptoms of pain or itching. You can judge based on these characteristics and compare your own situation.

Prickly heat is a common superficial, inflammatory skin disease in summer or hot environments. Because in a hot and humid environment, a large amount of sweat is not easy to evaporate, causing the stratum corneum to be soaked and swollen, and the sweat gland ducts to become narrow or blocked, resulting in sweat retention and sweat infiltration into the surrounding tissues, forming papules, blisters or pustules, which are more common in the folds.

Causes

Due to the high temperature and humidity in the environment, sweating is excessive and not easy to evaporate. Sweat soaks the stratum corneum of the epidermis, causing the opening of the sweat gland duct to narrow or become blocked. After sweat is retained in the sweat gland duct, it ruptures due to increased internal pressure. The overflowing sweat penetrates and stimulates the surrounding tissues, causing papules, papulovesicles and small blisters to appear at the sweat pores. Bacterial multiplication and toxin production can aggravate the inflammatory response. Some people believe that the blockage of sweat pores is due to primary staphylococcal infection, while others believe that the occurrence of prickly heat has nothing to do with excessive sweating, but is related to the massive proliferation of micrococci on the skin surface.

Clinical manifestations

According to the difference in sweat gland duct damage and sweat overflow site, it is clinically divided into the following types:

1. Crystalline Miliaria

Also known as white prickly heat, it is caused by the overflow of sweat in the stratum corneum or the sweat ducts under the stratum corneum. It is common in patients with high fever, heavy sweating, long-term bed rest, and excessive weakness. The skin lesions are superficial small blisters ranging in size from the tip of a needle to the head of a needle, with thin and clear walls, no redness around them, which break easily with slight rubbing and leave tiny scales after drying. It is self-limited and generally asymptomatic.

2. Red milia

Also known as prickly heat, it is caused by the overflow of sweat ducts in the spinous layer. The disease occurs acutely, with skin lesions appearing in batches as dense, round, pointed, needle-sized papules or papulovesicles, surrounded by a mild red halo. There is mild desquamation after the skin lesions subside. Conscious mild burning and itching sensation.

3. Pustular miliaria

Also known as purulent rash. It often develops from red miliaria. The lesions are dense papules with needle-sized superficial pustules on top. Pustules often contain sterile or nonpathogenic cocci.

4. Deep Milia

Also known as deep prickly heat, it is caused by the overflow of sweat ducts in the upper dermis, especially at the dermis-epidermis junction. It is common in patients with severe and recurrent episodes of red milia. The skin lesions are densely packed small skin-colored blisters with clear contents that are not easily rubbed, and they increase in size when sweating and decrease in size when not sweating. When the rash is widespread, sweating decreases or disappears on the skin of the whole body, and compensatory sweating increases on the face, armpits, hands and feet, which can cause tropical ahidrosis or heat exhaustion. Patients may experience systemic symptoms such as weakness, drowsiness, dizziness and headache.