Risk factors

Drug hypersensitivity reactions do not occur in everyone who uses a given drug and a variety of factors may increase the risk. In general, women are more susceptible, as are older individuals.1 People with more intact immune systems seem more prone to certain types of immune-mediated hypersensitivity. However, the rate of hypersensitivity is higher in people with HIV.2 Individuals who have experienced drug-induced hypersensitivity reactions in the past are more likely to do so again, as are people with a history of allergic conditions such as asthma.

For abacavir (Ziagen) hypersensitivity, risk factors seen in various studies include male sex, African ethnicity, more advanced HIV disease, and history of allergies.3 In one study of 50 HIV-infected people, nine developed a hypersensitivity reaction.4

Nevirapine (Viramune) hypersensitivity is more common in women and people with higher CD4 cell counts. Other risk factors include low body weight, co-infection with hepatitis B or C, and certain genetic patterns.5 6

Several types of hypersensitivity appear linked to genetic predisposition.7 Most patients with abacavir hypersensitivity carry the HLA-B*5701 haplotype.8 9 This genetic pattern may be present in as many as 10% of the population and is more common amongst Caucasians than people of African descent. For more information, see Antiretroviral therapy and hypersensitivity.


  1. Boulassel MR et al. Gender and long-term metabolic toxicities from antiretroviral therapy in HIV-1 infected persons. J Med Virol 78: 1158-1163, 2006
  2. Bayard PJ et al. Drug hypersensitivity reactions and human immunodeficiency virus disease. J Acquir Immune Defic Syndr 5: 1237-1257, 1992
  3. Symonds W et al. Risk factor analysis of hypersensitivity reactions to abacavir. Clin Ther 24: 565-573, 2002
  4. Stekler J et al. Abacavir hypersensitivity reaction in primary HIV infection. AIDS 20: 1269-1274, 2006
  5. Sulkowski MS et al. Hepatotoxicity associated with nevirapine or efavirenz-containing antiretroviral therapy: role of hepatitis C and B infections. Hepatology 35: 182-189, 2002
  6. Martin A et al. Predisposition to nevirapine hypersensitivity associated with HLA-DRB1*01 and higher CD4 T cell counts. 15th International AIDS Conference, Bangkok, abstract LbOrB13, 2004
  7. Pirmohamed M Genetic factors in the predisposition to drug-induced hypersensitivity reactions. AAPS J 8: E20-E26, 2006
  8. Mallal S et al. The presence of HLA-B*5701, -DRB*0701, and -DQ3 is highly predictive of hypersensitivity to the HIV reverse transcriptase inhibitor abacavir. Ninth Conference on Retroviruses and Opportunistic Infections, Seattle, abstract 91, 2002
  9. Martin A et al. Mapping of genetic susceptibility to abacavir hypersensitivity. Tenth Conference on Retroviruses and Opportunistic Infections, Boston, abstract 713, 2003
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.