What are the risks of going out in the morning with wet hair?

Another overlooked factor: residual moisture on the scalp after going outdoors with wet hair creates an environment conducive to microorganism growth. Certain yeasts, such asMalassezia, present on the skin surface, including the scalp, overgrow when the conditions become hot and humid —under a hat, hood, or with damp hair. This can lead to dysbiosis, an alteration of the bacterial ecosystem that can promote dandruff.

In fact, dandruff is a multifactorial condition associated with proliferation of Malassezia. These yeasts have lipase activity, meaning they hydrolyze triglycerides in sebum and release unsaturated fatty acids such as arachidonic acid. This metabolite triggers abnormal differentiation of keratinocytes in the stratum corneum. Arachidonic acid stimulates proinflammatory cytokine production. By this mechanism, Malassezia contribute to scale formation, redness, and sometimes itching of the scalp.

Going out with wet hair can affect hair appearance. The cortex is mainly keratin, a protein arranged in long chains stabilized by disulfide, ionic, and hydrogen bonds. Disulfide bonds, which form curls in some people, are strong, permanent covalent links. Once broken, for example by certain chemical straightening treatments, they do not reform. Ionic and hydrogen bonds are weaker. They break under water during washing but reform as hair dries, which allows temporary hairstyle hold.

Drying hair at home with a blow dryer or a towel helps define its shape.

Indeed, when hair dries in open air in a humid or windy outdoor environment, hydrogen bonds can reform in a disordered way, leading to a disordered strand arrangement and, in some cases, the appearance of frizz. This phenomenon affects textured or curly hair. It needs detailed care to maintain shape and avoid losing definition. Straight hair is not exempt and can develop cowlicks when drying in open air.

A common misconception is that going outside with wet hair causes a cold, yet this is not scientifically accurate. Cold or humidity do not cause winter illnesses such as the common cold or flu. In reality, these illnesses are viral in origin and spread through close contact with infected individuals, either via direct contact (handshakes, contaminated surfaces) or airborne droplets expelled when speaking, coughing, or sneezing.

That said, going outside with hair still damp in cold weather can cause a thermal discomfort and intensify the cool sensation at the scalp. This results from conduction: water on the hair promotes body heat loss, making the scalp more sensitive to low temperatures. Prolonged cold exposure, while not pathogenic in itself, can weaken local defenses in the nasal mucosa and increase vulnerability to infectious agents.

Going outside with wet hair does not cause illness itself. It can be uncomfortable in cold or windy weather and weaken immune defenses.