Hand, Foot, and Mouth Disease (HFMD) is a common, contagious viral illness caused by enteroviruses, most frequently Coxsackievirus A16, and primarily affects young children. The disease is characterized by a distinctive rash and sores in the mouth. A common concern for parents is whether these lesions will leave permanent marks, but in nearly all typical cases, the skin lesions associated with HFMD generally do not result in true, lasting scars.
Anatomy of the HFMD Rash
The HFMD rash begins with small, flat red spots, which rapidly evolve into small, fluid-filled blisters, known as vesicles. These lesions typically measure between 2 to 10 millimeters and often have an elongated, oval shape. The most characteristic locations for this rash are the palms of the hands and the soles of the feet, but lesions can also appear on the buttocks, knees, and around the mouth.
Simultaneously, painful sores or ulcers may develop inside the mouth, on the tongue, gums, and throat. These superficial skin eruptions are contained within the top layer of the skin, the epidermis, and do not typically damage the deeper tissue layers. The vesicles rupture, dry up, and then peel off without affecting the deeper dermal layer. The entire rash phase usually resolves on its own within seven to ten days.
Scarring Risk and Post-Inflammatory Marks
True scarring is rare with HFMD because the viral damage does not breach the basement membrane, which separates the top layer of skin from the deeper dermis. A true scar represents a permanent alteration of the dermal structure, which is generally not affected by the HFMD virus. However, the skin can sometimes display temporary discoloration in the areas where the lesions healed.
This temporary discoloration is known as post-inflammatory hyperpigmentation (PIH) or hypopigmentation. PIH causes a darkening of the skin, while hypopigmentation results in a lightening of the skin where the inflammation occurred. These marks are not scars and do not reflect permanent tissue damage, but rather a temporary change in melanin production triggered by the skin’s inflammatory response. Post-inflammatory marks will typically fade completely over a period of weeks or months.
True scarring is almost always limited to instances where the lesions are severely traumatized. Scratching, picking, or rubbing the blisters can cause a break in the skin that introduces bacteria, leading to a secondary bacterial infection. This deeper infection or trauma can disrupt the basement membrane and result in the formation of a permanent scar. Keeping the affected areas clean and preventing scratching helps ensure the lesions heal cleanly and without lasting marks.
Delayed Effects on Nails and Skin
Even after the primary rash has disappeared, HFMD can cause a few delayed, temporary effects on the skin and nails. One of the most common is peeling or desquamation of the skin, particularly on the palms and soles. This peeling often begins one to two weeks after the fever has resolved and is a normal part of the body shedding the outer layer of skin that was affected by the virus. The new skin underneath will heal and strengthen completely.
Onychomadesis involves the partial or complete shedding of fingernails or toenails. This phenomenon typically occurs four to six weeks after the initial illness. It is thought to be caused by the body’s systemic response, such as the fever or the virus itself, temporarily interrupting the function of the nail matrix, where new nail cells are made.
The old, affected nail plate separates and is pushed forward as a new, healthy nail begins to grow underneath. While this can look alarming, the condition is self-limiting and requires no specific treatment. The nails will regrow completely and look normal, though full regrowth of a fingernail can take three to six months, and a toenail may take up to a year.