The term “local” in dermatology refers to treatments applied to or conditions affecting a specific area of the skin. This is distinct from systemic approaches, where a substance enters the bloodstream and impacts the entire body. A local treatment acts only where it is applied, while a local skin condition is a problem that manifests in a limited area.
Mechanisms of Localized Action
The skin’s outermost layer, the epidermis, serves as a natural barrier that limits what can pass into the deeper layers and the bloodstream. The structure of the epidermis, particularly the stratum corneum, is a tightly packed layer of cells and lipids that resists penetration. This barrier ensures that substances applied to the surface have a limited ability to travel deeper into the body.
The formulation of a topical product is engineered to work with this natural barrier. The chemical and physical properties of creams, ointments, gels, and patches control how an active ingredient is delivered. The goal is to keep the medication concentrated at the site of application, maximizing its effect on the targeted skin tissue while minimizing absorption into the systemic circulation.
Types of Local Skin Treatments
Local anesthetics are a common category of local treatment used to numb a specific area of the skin before minor procedures. Formulations containing agents like lidocaine are applied to temporarily interrupt nerve endings in the skin. This action blocks pain signals at their source, preventing them from reaching the brain.
Topical corticosteroids are another class of local treatments designed to reduce inflammation, redness, and itching associated with inflammatory skin conditions. When applied to an affected area, these substances suppress the local immune response causing the symptoms. The medication penetrates the upper layers of the skin to act on the cells involved in the inflammation.
Topical antimicrobials, including antibiotics and antifungals, are applied directly to the site of a skin infection. An antibiotic ointment delivers its drug to the bacteria on the skin’s surface. Similarly, antifungal creams target fungi causing conditions like athlete’s foot or ringworm, concentrating the treatment where the microbes are growing.
Localized Skin Conditions
Many skin conditions are inherently local, confined to a specific area. Contact dermatitis is a clear example, occurring when the skin touches an irritant or allergen like poison ivy oil or nickel. The resulting rash, redness, and itching are restricted to the exact area of exposure.
An insect bite is another example, producing a reaction like swelling or itching only at the specific spot. The body’s inflammatory response is concentrated at the site of the bite. Warts, which are small viral skin growths, also appear in specific locations and are treated by targeting only the affected tissue.