The skin, the body’s largest organ, acts as a primary interface between internal systems and the external environment. Given its visibility, it frequently displays reactions to foreign substances, including medications and recreational drugs. These substances can alter the skin’s structure and function, ranging from mild inflammation to life-threatening immune responses. The skin often provides the first outward sign of an internal drug reaction. This article surveys how medications and other substances can affect the skin’s health and appearance.
Common Dermatological Side Effects
Many common prescription and over-the-counter medications can trigger mild to moderate skin reactions. The most frequent are maculopapular rashes, which appear as flat, red or pink spots mixed with small, slightly raised bumps. These rashes are not usually severe and often resolve once the body adjusts to the medication.
Another common reaction is generalized urticaria, also known as hives, which presents as intensely itchy, raised welts or plaques. Pruritus, or generalized itching without a specific rash, is also a frequent side effect, often caused by the drug interfering with chemical mediators. These reactions are typically manageable and disappear when the drug is discontinued or the dosage is adjusted.
Some medications can affect the sebaceous glands, leading to changes in oil production. Drug-induced acne occurs when certain drugs, such as corticosteroids, trigger a breakout of pimples and pustules. Conversely, other drugs may cause excessive skin dryness, leading to scaling and cracking.
Drug-Induced Sensitivity to Sunlight
A distinct adverse reaction occurs when a drug makes the skin abnormally sensitive to ultraviolet (UV) radiation. This condition, known as photosensitivity, requires both the drug’s presence and subsequent light exposure to cause a reaction. Photosensitivity reactions are categorized into two main types based on their mechanism.
Phototoxicity
Phototoxicity is the more common type, occurring when the drug absorbs UV light and releases energy that directly damages skin cells. This reaction is dose-dependent; higher drug concentration or longer sun exposure increases the risk. It clinically resembles an exaggerated and severe sunburn. Certain systemic drug classes, including some antibiotics (like tetracyclines and fluoroquinolones) and certain diuretics, are known to cause phototoxicity.
Photoallergy
Photoallergy is a less common, immune-mediated response that develops after sensitization to the drug. UV radiation alters the drug’s chemical structure, causing the immune system to recognize it as a foreign invader. Photoallergic reactions typically manifest as a delayed, eczema-like rash that can spread beyond the sun-exposed areas. This type is often associated with topical nonsteroidal anti-inflammatory drugs (NSAIDs).
Recognizing Severe and Systemic Reactions
While most drug-related skin issues are mild, a few rare but serious reactions constitute dermatological emergencies requiring immediate medical intervention. These severe cutaneous adverse reactions (SCARs) involve the skin and often internal organs. Early recognition is paramount to preventing potentially fatal outcomes.
Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN)
SJS and TEN are life-threatening reactions considered variants of the same disease. They often begin with flu-like symptoms, followed by the rapid onset of a painful, blistering rash and the involvement of mucosal surfaces (e.g., mouth and eyes). SJS involves skin detachment affecting less than 10% of the body surface area, while TEN involves detachment of over 30%, resulting in sheet-like skin loss.
DRESS Syndrome
Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome can present weeks after starting a medication. It is characterized by a generalized rash, high fever, and the involvement of internal organs (e.g., liver or kidneys). Eosinophilia, an elevated count of a specific type of white blood cell, is a distinct laboratory feature. Both SJS/TEN and DRESS syndrome are medical emergencies requiring hospitalization to manage fluid loss, infection risk, and multi-organ failure.
The Consequences of Illicit Drug Use
The use of illicit substances introduces a unique set of dermatological problems stemming from mechanical trauma, infection, and the drug’s direct pharmacological effects. For individuals who inject drugs, repetitive needle use and poor sterile practices lead to specific complications at injection sites. These include hyperpigmented scars, colloquially known as “track marks,” which result from post-inflammatory changes.
The injection of non-sterile substances can introduce bacteria, leading to soft-tissue infections such as cellulitis and abscesses. These infections are common when users “skin pop,” or inject the substance just under the skin instead of directly into a vein. The chemicals and cutting agents in illicit drugs can also cause vascular damage, leading to tissue necrosis and ulcerations.
Certain stimulant drugs, such as methamphetamine, can induce formication, a tactile hallucination that feels like insects crawling under the skin. This sensation often provokes compulsive scratching and skin picking, resulting in self-inflicted wounds. These open sores, frequently referred to as “meth sores,” increase the risk of secondary bacterial infections and leave behind characteristic scarring.