The skin on the lips is distinct from the rest of the face because it is significantly thinner and lacks the oil-producing sebaceous glands that help lock in moisture. This anatomical difference makes the lips highly vulnerable to both internal and external changes. When the body is fighting an infection, the stress and resulting physical and behavioral factors disrupt the delicate moisture balance, leading quickly to dryness and chapping.
Systemic Dehydration and Fluid Loss
When a fever is present, the body’s metabolic rate increases, leading to a greater rate of insensible water loss through the skin and respiratory tract. For each degree Celsius rise in body temperature above normal, an adult can lose an additional 2.5 milliliters of fluid per kilogram of body weight per day through evaporation alone. This loss, which can be compounded by significant dermal water loss from sweating, can amount to an extra 500 to 1,000 grams of water lost over 24 hours during high fever.
The fluid deficit is worsened by a decrease in fluid intake, as many people experience reduced appetite or nausea when ill. When internal hydration levels drop, the body redirects available water to prioritize the function of vital organs. The skin is one of the first areas to lose moisture, causing the lips to dry out quickly. This systemic fluid depletion makes the lips brittle and less able to withstand external drying factors.
Respiratory and Behavioral Contributors
When nasal passages are blocked due to congestion, the body reflexively switches to mouth breathing. Constant exposure to the flow of air across the lips accelerates the evaporation of moisture from the thin outer layer of skin. This continuous exposure is especially drying in environments with low humidity, quickly leading to a loss of the skin’s natural barrier function.
Behavioral changes also play a significant role in exacerbating lip chapping. The friction caused by frequently wiping or blowing the nose can mechanically irritate the surrounding skin and the lips themselves. Licking the lips is a common, though counterproductive, habit: saliva contains digestive enzymes and, as it evaporates, it draws even more moisture from the lip surface, leaving the lips drier than before.
Medication Side Effects and Inflammation
Many common over-the-counter cold and flu treatments contribute to dryness as a known side effect. Decongestants, such as pseudoephedrine, work by acting as sympathomimetic agents that stimulate alpha-adrenergic receptors, causing vasoconstriction in the nasal passages. This constricting action reduces swelling and fluid production in the mucous membranes to relieve congestion. However, this drying effect is not selective and can lead to general dryness of the mucous membranes in the mouth, nose, and throat.
Antihistamines, frequently included in multi-symptom medications, further contribute to generalized dryness by reducing secretions throughout the body. Beyond medication, the body’s overall inflammatory response to infection can also impair the skin barrier function. Systemic inflammation involves the release of cytokines, signaling proteins that affect the integrity of the epithelial barrier, making the lips more susceptible to moisture loss and irritation.
Prevention and Relief Strategies
Consistent intake of fluids, like water and electrolyte solutions, helps address the increased fluid loss associated with fever and illness. Using a cool-mist humidifier in the bedroom can counteract the drying effects of forced air heating by increasing the moisture content of the air around the lips during sleep.
Topical treatment involves creating a protective barrier on the lips to seal in moisture and prevent further evaporation. Thick ointments containing white petrolatum or dimethicone are highly effective occlusive agents that physically block water loss. Products containing ingredients like ceramides or castor seed oil can also help support the lip’s natural barrier function.
It is helpful to avoid lip balms that contain ingredients known to cause further irritation or drying, such as menthol, camphor, phenol, or strong flavorings. These agents may provide a temporary cooling sensation but can ultimately exacerbate the chapping cycle. Instead of licking dry lips, applying a non-irritating, fragrance-free ointment immediately can help break the cycle of irritation and promote healing.