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Hay Fever Makes Your Brain Go Out of Control; So Don't Drive When You Have An Allergic Reaction

(Image: Aldo Sperber/picturetank - from New Scientist )
Thirty per cent of the adult population experience seasonal allergies, especially hay fever. The eyes start watering and reddening and noses start running, making you looking and feeling like a big mess. But did you know that these are not the only effects of allergies? Did you know that it affects your brains reaction time to driving too?

Hay fever or allergic rhinitis can be aggravated by anything from pollen, mould, dust, fungal spores or animal dander; they aggravate the immune system inappropriately to harmless substances / allergens. 

False Alarms...

When a pollen grain lands on the damp lining of the nose and throat, its tough outer coat can burst, releasing its contents, including allergenic proteins. These come into contact with immune cells called mast cells, which are the body's first line of defence against invaders. 

In most people, these harmless proteins are ignored, but those with allergies are not so lucky. Receptors on the surface of their mast cells bind to the offending proteins, prompting an immune response. 

The body starts to produce antibodies, called IgE antibodies; that are specific to the type of allergen they will be "attacking" (such as pollen, mould, dust, fungal spores or animal dander). 

Thousands of these antibodies bind to the surface of special cells in body tissue called mast cells, which then lie in wait for your next exposure to that specific allergen. During this wait, these mast cells absorb many different chemicals from the blood that will aid in the body's defence; they then store these chemicals in minuscule granules. When you're re-exposed to the allergen, the allergen binds to the IgE antibodies on the surface of the mast cells, causing the mast cells to release the chemicals. One of the chemicals, histamine, which I’m sure everyone has heard of; is one of the biggest players in the allergic response system and is the initiator of many of the allergic symptoms, such as runny nose, sneezing, and itchy and watery eyes.

Anti-histamine medications block histamine from binding to its receptor. The allergic reaction can have both an early and a late phase. Typically the early phase may start within a few minutes of exposure, while the late phase may start several hours after the initial exposure. The early phase is caused by the release of those chemicals stored in the granules in the mast cells. The late phase reaction is caused by other inflammatory cells recruited into the area.

Previous studies have shown that allergic rhinitis affects cognitive function and especially in more complex tasks. This study looks at the effect of allergic rhinitis (AR) on driving performance and driving reaction times in particular.

The method they undertook...

Nineteen patients with documented AR history underwent a unique and validated 1-h on-the-road driving test outside the pollen season. In a 4-leg repeated measures design, patients underwent a nasal provocation test with either pollen or inactive control prior to the driving test. In the three conditions with pollen provocation, patients were pre-treated with either cetirizine 10 mg, fluticasone furoate 27.5 μg, or placebo to alleviate the provoked AR symptoms.

The results they found...

They found that untreated AR definitely impaired reaction times compared to the placebo condition.  When they were required to do a secondary memory task during driving, their performance deteriorated further. They found that their impairment was as if they had "a blood alcohol level of 0.05%" which is the legal limit in many countries. However they found that treating AR significantly counteracted these effects, showing that it absolutely essential to treat AR symptoms for your safety and peace of mind. 

Vuurman EF, Vuurman LL, Lutgens I, & Kremer B (2014). Allergic rhinitis is a risk factor for traffic safety. Allergy, 69 (7), 906-12 PMID: 24815889