Hay fever: Why are some people allergic to pollen

Spring brings blooming flowers and trees. Butfor people who struggle with pollen allergies, those flowers may bring onsymptoms such as sneezing, runny nose and itchy eyes.

"Well over one million Norwegians pick upprescription allergy medicines every year," says Anna Bistrup, a senior adviserfor health and public relations at the Norwegian Asthma and Allergy Association(NAAF).

"That's a really high number, and we knowthat many of these people are allergic to pollen," she says.

That figure does not include those who buyover-the-counter allergy medicines.

Pollen allergies can have a significantimpact on the quality of life for some allergy sufferers. But why are somepeople are allergic to pollen, while others are not?

Pollen allergy is the most common allergy type.It typically causes symptoms in spring and summer. Pollen itself is notdangerous, but our immune system doesn't know that.

"When you are allergic, the immune systemoverreacts by making antibodies against something that is not really dangerous.Your immune system identifies the allergen as something dangerous, even if itis not, and initiates an ‘immune response’, where the body produces histamines,among other things. Those are what cause the allergic symptoms," Bistrup said.

There is also a higher risk of developingallergies if one or both parents have allergies.

"We can say that if neither parent of a childhas allergies, then the chance that the child will develop allergies is justunder 20 per cent. If one of the parents has allergies, the risk increases to45 per cent. If both parents have allergies, there is an 80 per cent chance thatthe child will also have allergies," says Sverre Steinsvåg, a chief physician in the ear-nose-throat department at Sørlandet Hospital and HaukelandUniversity Hospital and professor at the University of Bergen.

Steinsvåg also highlights the way we live asa factor in why some people develop allergies.

"We now live in a manner that means that weare much less exposed to microorganisms, especially bacteria. For example, wepurify our water, heat milk and use antibiotics early in life. These factorsmean that we are no longer exposed to microorganisms, and in concert with that,the incidence of allergies has increased," he says.

In many ways, he says, pollen allergies are alifestyle disease. We have chosen to live in a way where bacteria are less of apart of our lives.

Another factor that plays into this trend isthat people spend much less time outdoors than they once did.

"Now to a much greater extent than before, wedo everything, from homework to play, in front of screens. The consequence ofthat is that we spend much more time indoors and in houses. Then we go outside and are exposedto everything from food allergens and pollen allergens to animal allergens. Theincidence of allergies has increased as a result," Steinsvåg says.

He also points out that we are exposed toless sun when we are indoors, which can mean that we have less protection againstallergies.

"Vitamin D is very protective againstallergies, so when we don't get sun, we don't make much vitamin D, so we haveless protection against allergies," says Steinsvåg.

Around 25 per cent of Norway's population hasa pollen allergy, Steinsvåg said.

"There is no difference when it comes togender, but this is typically a disease for slightly older children and youngadults. Many people will ‘grow out of it’, but certainly not all. We also seemajor pollen problems in mature adults, but it seems to be a bigger problem foryoung adults," he says.

Most people with pollen allergies in Norwaystruggle with birch and grass pollen. Bistrup says that 20 per cent of peoplewho are allergic to birch also react to other types of pollen from tree speciessuch as alder, hazel and willow.

Pollen allergy symptoms typically include a runnyor stuffy nose, itchy eyes, red and swollen eyes and itchy mouth. Bistrup alsosays that some people can have an allergic asthma reaction during the pollenseason, which creates a reaction in the lungs. Many people also get headachesand feel ill.

Some people are more allergic thanothers. Bistrup says allergies span a large spectrum.

"There are some who are just a little itchy andfind that it will be fine. Other people become quite unwell and feel that theallergy affects their everyday life throughout the season. There are alsopeople who have to travel to another area where there is less pollen or travel abroadto get a break from their allergic problems," she says.

There is no simple explanation as to why somepeople are more allergic than others, but Bistrup says that the answer relatesto you as an individual, your body and your immune system.

If a person is allergic to one thing, it canbe easy to think that person has other allergies as well. Do people with pollenallergies have a greater risk of developing other allergies, such as to certainfoods?

"Pollen allergies are very common and mostsufferers don't have other allergies, but there can be respiratory allergens.We distinguish between food allergens, respiratory allergens and contactallergens. Respiratory allergens are things like pollen, mould, fur animals andmites. These are allergens that spread in the air. Pollen allergy is arespiratory allergy that is different from a food allergy," Bistrup says.

People can also develop what is called a ‘cross allergy’. Bistrup says that some pollen allergy sufferers canexperience mild but unpleasant reactions after eating certain foods, such asraw fruit, vegetables, spices or nuts. But this shouldn't be confused with afood allergy, she said.

Cross allergies occur when the protein in thefood you eat is similar to the pollen protein you are allergic to. Thisoverreaction is generated by the immune system, which causes problems andsymptoms such as itching and irritation in the mouth.

Sometimes pollen allergy sufferers may findthat they were more or less allergic in the previous season. Bistrup says thisis due to how the pollen spreads.

"This year, for example, it is expected thatthe birch will spread more pollen than it did last year. In certain years,certain trees and grasses release more pollen, which results in more exposure,"she said.

Bistrup also says that other factors can playa role. If, for example, someone with pollen allergies is ill due to somethingelse during pollen season, they may have a stronger reaction to the pollen.

Bistrup says that it is important to rememberthat there treatments beyond just allergy pills.

"There are allergy-specific nasal sprays thatcontain antihistamines. There are also prescription nasal sprays that containcortisone, which helps to dampen the inflammatory reaction in the mucus membranesin the nose," she said.

If a person with pollen allergies has a lotof problems and normal medicines don't work as well as they would like, it isalso possible to ask your doctor about the possibility of allergy vaccinations.

Steinsvåg says that far too few are offeredallergy vaccinations in Norway today.

"It appears that too few patients are awareof this treatment, so they don't ask their doctor about it. There also appearto be too few doctors who know how effective this treatment can be. So we havea major job to here to inform people, which we do as best we can," he says.

Steinsvåg says that researchers have reliablefigures that show that people who have gone through a pollen vaccination schemehave very good outcomes from the treatment.

Steinsvåg says the only way to possibly curepollen allergies is pollen vaccination.

So what can allergy sufferers do to getthrough this year's season?

Bistrup says that it's important to preparefor allergies before the spread of pollen starts. She recommends that people check out the Norwegian Asthma and Allergy Association's national pollenwarning and pollen calendar. Other countries likely have similar associationswith this kind of information. These tools can be used to monitor theapproximate start of the pollen season.

Steinsvåg says the most important thing is toavoid spending time in areas where there is a lot of pollen. That's easier saidthan done, since pollen can spread over long distances.

It is also important to use allergymedicines in the correct way. They should be used daily during the peak pollenperiod, in spite of whether it's raining or snowing, or if the symptoms lastless than one day. The recommendation is that people should use these medicinesthroughout the pollen season. If this does not work, Steinsvåg recommendsallergy vaccination as an alternative.

Translated by Nancy Bazilchuk

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Read the Norwegian version of this article at forskning.no