People who are allergic to mold are at higher risk of suffering hair loss when exposed to this allergen. Allergic reactions, causing hair loss, can be triggered by both black "toxic" mold or other molds found in the house.

Allergic reactions cause the body to produce histamine, an inflammation-causing substance that results in the disruption of blood flow to the capillaries. The capillaries in the scalp nourish the hair follicles. Hair loss may result when blood flow to these capillaries is disturbed as a result of an allergic reaction to mold. Hair loss, in this case, will be diffuse over the entire head

Hair loss can also result from fungal infections in the scalp, caused by constant exposure to mold spores in the house. In this case the mold infects the out layer of the skin, leading to rashes, scaling, small sores and other visible symptoms, which in turn can lead to patches of hair loss.

To reverse the hair loss, the first step is to remove mold from the house. If the exposure to mold has been limited and has not resulted in the death of the hair follicles, the hair loss caused by allergies to mold, or by fungal infections on the scalp, can be reversed.