Kelly McSweeney

Mar 24th 2021

Links Between Allergic Reaction and Immune System Genetics


The human body’s immune system is meant to defend against foreign invaders, but sometimes it gets confused. When we take medicine such as antibiotics to treat infections, our defense system can go into overdrive, causing hypersensitivity or an allergic reaction. Why can some people tolerate medicine while others break out in hives or sometimes even have a severe reaction called anaphylaxis? A recent genetics study found links suggesting that some people could be predisposed to medication allergies.

The Penicillin Study

Antibiotics are one of the most common causes of drug-related allergic reactions, with penicillin being the most prevalent. Reactions can range from mild (rash) to severe (anaphylaxis). According to the Centers for Disease Control and Prevention (CDC), 10% of people report penicillin allergies, although only 1% of the population are truly allergic. Technical definitions aside, many people say they have experienced hypersensitivity to the medicine, such as rashes, nausea, wheezing and cardiovascular problems. Meanwhile, the remaining 90% of people are able to take the antibiotic without issues.

To find out why some people are hypersensitive to the drug, researchers at the Estonian Genome Center at the University of Tartu combed through 600,000 electronic health records, as Science News reports. They found an association between people who said they were allergic to penicillin and a specific gene variant. The researchers also confirmed their findings by checking large banks of DNA samples. Again, they came to the same conclusion: People with self-reported penicillin allergies often have a genetic variation on an immune system gene.

Role of HLA Genes in Drug Reactions

The study has wider implications. It can help us begin to understand connections between allergies and genetics. The National Library of Medicine explains that HLA-B is part of a family of genes called the human leukocyte antigen (HLA) complex. These genes provide “instructions for making a protein that plays a critical role in the immune system.” Proteins are large, complex molecules that are often called the building blocks of life. They are so abundant that our bodies need to sort out good proteins from bad ones.

HLA genes help our immune system differentiate between our body’s own proteins from those proteins made by foreign invaders, such as viruses and bacteria. There are hundreds of versions (alleles) of the HLA-B gene, each with a specific purpose and a number to identify it. The Estonian study, for example, linked penicillin allergy to a chromosome 6 variant called HLA-B*55:01.

In addition to penicillin, people can be allergic to other medications. Science News points out that other studies have also connected HLA genes to bad reactions to abacavir, an HIV/AIDs drug, and a gout medication called allopurinol.

Allergies and Genetics

We can’t say that an allergic reaction is caused by genetics, but understanding genetics can help us be aware that we may be predisposed to conditions such as allergies. This is an example of precision medicine, which uses genetics to find out the best possible treatment for each patient.

DNA tests could help people find out if they are likely to be allergic to medication so that they can work with their healthcare providers to assess risks and consider alternative medicines, if necessary. As we continue to learn more about the links between genetics and the immune system, doctors and scientists can ensure that people receive the right medication for their specific needs.