Amsterdam institute for Immunology and Infectious diseases

With rising temperatures, hay fever symptoms are increasing. It seems more people are suffering during allergy season, but is that true? Prof. dr. Thomas Rustemeyer, a dermatologist at Amsterdam UMC and member of the AI&I immunology program, along with Maurits van Maaren MSc, an internist, allergist and clinical immunologist at Erasmus MC, answer the six most frequently asked questions about hay fever.

1. Are more people developing hay fever?

Prof. Rustemeyer, a dermatologist at Amsterdam UMC: “Yes, more people develop hay fever each year due to epigenetic changes, which alter how our bodies use genetic information without changing DNA. Factors like lifestyle, sleep, alcohol, smoking, stress, and exercise impact our bodies. Climate change, pollution, PFAS, and fine dust exposure also play roles in allergy development, causing a 10-15% annual increase in hay fever cases.”

van Maaren, an internist, allergist, and clinical immunologist at Erasmus MC, adds: “Environmental factors like diet, antibiotic use, air pollution, soap or disinfectant use, and growing up in urban versus rural areas also affect the likelihood of developing allergies like hay fever.”

2. Is hay fever hereditary?

Prof. Rustemeyer: “Yes, hay fever, along with allergic asthma and eczema, is an atopic condition. Atopic people often have multiple allergies simultaneously, known as the atopic syndrome. If one parent has an atopic condition, there’s a 40-50% chance their child will too; if both parents have it, the chance is 70%. Even if neither parent has an allergy, there’s still a 20% chance for the child.”

Van Maaren: “Hereditary predisposition certainly plays a role, but besides that some people are more predisposed to develop allergic conditions like eczema, hay fever, or asthma than others.”

3. Why do some people get severe hay fever while others don't?

Prof. Rustemeyer: “Hay fever is an overreaction of the immune system to substances that don't belong in the body. The immune system must decide if each substance is a friend or foe. This selection isn't always precise, so harmless substances like tree pollen can be seen as foreign. This immune reaction to allergens causes allergic reactions. Everyone’s immune system reacts differently due to genetic and environmental factors. Younger people tend to have more active immune systems, hence more allergies develop in childhood. Interestingly, having hay fever indicates a well-functioning immune system, which is crucial in regions with life-threatening parasites.”

4. Why does hay fever sometimes develop later in life?

Prof. Rustemeyer: “While hay fever usually develops in children aged 6-8, it can develop at any age and is common among adults. Eczema in young children often precedes allergy development, disrupting the skin barrier and leading to food allergies, and potentially hay fever and asthma later. This is why controlling eczema early is important, as developing one allergy increases the risk of others, even in later life.”

5. Can hay fever be prevented?

Van Maaren: “You can't completely prevent hay fever. You can’t change genetic predisposition, but you can minimize it by optimizing the environment early. Modern lifestyles with less outdoor play, more screen time, frequent hand washing, and cleaner environments lead to bored immune systems, which are more likely to react to allergens. Encourage children to play outside, exercise, and interact with livestock and farmland. Avoid fast food, provide yogurt and fish, and limit unnecessary antibiotics. Reduced contact with disinfectants is also crucial. Expose children to potential allergens like pollen and house dust mites from 11 months old, and introduce foods that commonly cause allergies (peanuts, nuts, milk, eggs) three times a week for five years, especially if there’s a family history of allergies.”

6. Can hay fever be cured?

Prof. Rustemeyer: “Curing hay fever is challenging, but effective treatments are available. Safe medications like pills, eye drops, and nasal sprays can alleviate symptoms. Immunotherapy is an option for severe cases, involving small doses of allergens (like grass pollen extract) over three years through injections or daily dissolvable tablets. This helps the body gradually stop reacting to allergens, reducing symptoms.”

Van Maaren: “Many people experience fewer symptoms after age 50, but not everyone. Injections and tablets are equally effective. The advantage of allergen-specific immunotherapy is its lasting effect after a three-year treatment, unlike medication that works only with daily use. This intensive and expensive treatment is for those who still suffer despite medication. Staying by the coast also helps reduce pollen exposure, as long as the wind comes from the west; otherwise, pollen from inland can still affect you.”

Source: this article is a revised version of an article originally published in Dutch on DeMorgen.be, authored by Elleke van Duin. Access the original piece here.