Researchers in Denmark have identified a subgroup of allergic reactions that may explain why some people react much more quickly to contact allergens than other people.
In a July 13, 2021 press release from the University of Copenhagen, where the research was conducted, the investigators note that immediate and delayed allergic reactions have traditionally been distinguished depending on which parts of the immune system are responsible for the reaction.
However, they say the findings from their new study, published online ahead of print in Allergy (June 25, 2021), may change the medical understanding of contact allergy.
“Some patients develop allergic contact dermatitis at a much earlier stage than described by textbooks. The aim of the study was therefore to try to determine why some react to contact allergens much faster than [expected],” said the study’s first author PhD student Anders Boutrup Funch, in the release. “It turns out that when a part of the skin is exposed to the allergen for the first time, the cells within that specific skin area will develop local memory towards the contact allergen. And then when the same area is re-exposed to the allergen at a later point in time, the patient will develop a clear reaction within only 12 hours.”
In the study, which was conducted in animal models, the researchers were able to show that T cells in the body—responsible for delayed allergic reactions or ‘Type 4’ reactions—are also able to develop a ‘memory’ to contact allergens that allow them to respond much faster to re-exposure than previously assumed.
“We point to a need for clarification of this disease. Type 4 reactions should be subcategorized, giving us both the classic delayed reaction—that is, where the patient reacts 24-72 hours after exposure—and an immediate reaction, where the patient develops symptoms much faster,” said the study’s senior author Professor Charlotte Menné Bonefeld, in the release. “Based on these results, we may have to change the textbooks on contact allergy. At any case, we will need to add a chapter.”
Dr. Bonefeld is a professor at the Skin Immunology Research Center at the University of Copenhagen.
The research also showed that activation of memory T cells following allergen exposure leads to massive recruitment of neutrophils to the affected part of the skin. Skin infiltration of these neutrophils leads to the local inflammation patients experience as a rash. The authors note that neutrophil recruitment is not seen in connection with delayed reactions to contact allergens.
To build on their findings the authors say the next step will be to test the study results on humans.