According to the European Academy of Allergy and Clinical Immunology around 150 million people in Europe suffer from one allergy or other, in the US allergies are the sixth leading cause of chronic illness and leads to healthcare costs in excess of $18 billion each year.

Now, researchers from Germany and Switzerland say there could be possible associations between conditions relating to mental health, such as depression and anxiety, and the presence of different types of allergy.

Certain allergic conditions have been shown to affect a person’s mental health. For instance, last year one study found that having asthma, allergic rhinitis, or atopic dermatitis (eczema) could increase a person’s risk of developing a mental illness.

Now, researchers from the Technical University of Munich (TUM) in Germany have collaborated with investigators from other German and Swiss institutions to investigate this association further. The team recruited 1,782 participants and aimed to find out if there were any links between mental health conditions, such as anxiety and depression, and different types of allergy.

The study participants were between the ages of 39 and 88 years, with 61 years being the average age.

For their study, the researchers only took into account cases of type 1 allergies. These are allergies that cause an immediate reaction following exposure to the allergen, and they can result in symptoms of varying severity. They range from eczema and hay fever, also called allergic rhinitis, to conjunctivitis and anaphylaxis.

In the study, the investigators differentiated between participants according to their type of allergy (or lack thereof), splitting them into four distinct groups: those who were allergy-free; those with seasonal allergies, such as those relating to pollen; those with perennial (year-long) allergies, such as allergies to animal hair; and those people with other allergies, including allergies to foods and insect stings.

Within the entire cohort, 27.4 percent of the individuals reported having an allergy. More specifically, 7.7 percent of participants said that they had a perennial allergy, 6.1 percent had a seasonal allergy, and 13.6 percent reported having another type of allergy.

After asking the participants additional questions about their mental health — focusing on markers of depression, generalized anxiety disorders, and stress — the researchers concluded that individuals who lived with generalized anxiety also tended to have seasonal allergies.

This association was not present in people with perennial allergies. However, the study showed that individuals with year-long allergies were more likely to have depression instead.

It remains unclear why there is a positive association between anxiety and seasonal allergies but not between this mental health condition and perennial allergies. The researchers are also unsure why the latter more often link to depression.

In the future, the researchers note, scientists should conduct further studies to find out which way the association lies — whether specific allergies increase the risk of certain mental health problems or vice versa — and why it exists in the first place.

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