CIRCUMSTANCES AND CHARACTERISTICS: The risk of toxiderma is greater in patients infected by the human immunodeficiency virus (HIV). The most common toxidermas are maculopapular exanthema and drug hypersensitivity reactions. These toxidermas are predominantly observed with non-nucleoside reverse transcriptase analogs (nevirapine, efavirenz) and abacavir. Toxiderma has also been observed with other nucleoside reverse transcriptase analogs (zalcitabine) and protease inhibitors. REGARDING SEVERITY: The toxidermas observed are usually benign (maculopapular exanthema) and do not always require suspension of the treatment. However, certain toxidermas (Stevens-Johnson syndrome, Lyell syndrome and drug hypersensitivity syndrome) may be life-threatening and therefore contraindicate the continuation of treatment and also its sudden reintroduction. PREVENTION AND PRACTICAL APPROACH: Several studies have assessed the risk factors for toxiderma induced by nevirapine and hypersensitivity reactions to abacavir. The practical approach varies depending on the drug responsible, the clinical form of the toxiderma and the possible alternatives.