Is dandruff contagious?

Dandruff is one of the most common scalp conditions, affecting approximately 50% of the adult population worldwide. It is characterized by an excessive desquamation of the scalp skin, which leads to the appearance of fine particles, sometimes accompanied by itching. Two types of dandruff : greasy, yellowish, sticky flakes, which are the most frequent and are associated with an oily scalp, and dry, fine, white flakes that tend to fall like snow on the shoulders.

Several factors can contribute to the formation of dandruff. Sebum production in particular plays a key role by creating an environment conducive to the growth of certain microorganisms. Factors such as stress, hormonal fluctuations, pollution, or the use of unsuitable hair care products can also alter sebaceous gland activity and exacerbate flaking. However, the core of the dandruff formation process involves a fungus naturally present on our scalp : Malassezia.

This lipophilic fungus is part of the scalp’s cutaneous microbiota. Under normal conditions, it coexists with the skin without causing discomfort. However, under certain circumstances—particularly in the presence of excess sebum—it multiplies and releases enzymes capable of breaking down sebum triglycerides into free fatty acids. These molecules then penetrate the stratum corneum and cause local irritation. The resulting inflammation disrupts the normal cycle of cell renewal : the scalp’s skin then renews itself too rapidly, leading to an accumulation of dead cells in the form of visible flakes.