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Allergies can impair cognitive functions, especially during longer-lasting tasks. Other reports suggest negative effects on psychomotor functions such as driving, but no clear evidence has been presented yet, San Diego DUI lawyers learned in the study in this article.

It may not be surprising that common seasonal allergy symptoms, such as watery eyes, sneezing and fatigue, can significantly impair driving ability, says a study in the July issue of Allergy. Allergy symptoms’ effect on driving was comparable to having a blood-alcohol concentration nearing impaired levels, according to the researchers.  Allergy medications weren’t wholly effective at reducing the symptoms’ effects.
Allergic rhinitis, or hay fever, has been linked to car accidents but the effects on a driver’s performance weren’t known, researchers said.
The study, in the Netherlands, involved 19 people in their early 30s with grass- and tree-pollen allergies. During the off-season, when they were free of symptoms, subjects were each treated in turn with an antihistamine, steroid nasal spray or a placebo pill or spray in four testing sessions on separate days. After each treatment, they were given grass and tree allergens or a placebo through a nasal spray to provoke allergy symptoms.
The subjects then did a 60-minute driving test in a vehicle with a camera that recorded how often they veered toward the center lane. The technique, called standard deviation of lateral position (SDLP), is commonly used to assess drunken driving. The higher the SDLP score, the greater the impairment. During the last 15 minutes of driving, subjects were given verbal memory tests where they were asked to recall as many words as possible from a list presented through the car audio system.
The greatest impairment occurred in participants with allergic symptoms who had received a placebo treatment. SDLP scores for this group were comparable to driving with a blood-alcohol level of 0.03%, just under the legal limit of 0.05% in most countries, researchers said. (The U.S. limit is 0.08%.) Both the antihistamine and nasal spray reduced SDLP scores to nonsignificant levels.
Driving scores of allergy sufferers deteriorated further during the memory tests. In this case, only treatment with nasal spray improved SDLP scores. The antihistamine’s effects were comparable to placebo, possibly because of additional mild sedation due to the drug, the researchers said.
Caveat: Participants were tested in easy driving conditions, without distraction from cellphones, radios, or bad weather. The study was partially funded with a grant from GlaxoSmithKline.
Title: Allergic rhinitis is a risk factor for traffic safety:


Allergic rhinitis (AR) affects up to 30% of the adult population and symptomatic patients continue to engage in daily life activities, including car driving. Previous studies have shown that AR can impair cognitive functions, especially during longer-lasting tasks. Other reports suggest negative effects on psychomotor functions such as driving, but no clear evidence has been presented yet.


Primary objective was to determine the effect of AR per se on actual driving performance and compare it with the effects of treated AR.


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 pretreated with either cetirizine 10 mg, fluticasone furoate 27.5 μg, or placebo to alleviate the provoked AR symptoms.


The driving performance of patients when symptomatic and not treated was significantly impaired compared to the placebo condition. When engaging in a secondary memory task during driving, their performance deteriorated further. The magnitude of impairment was relevant and comparable to that seen at a blood alcohol level of 0.05%, the legal limit in many countries. Treatment of AR symptoms partially counteracted the effect of AR on driving.


Untreated AR can impair driving ability and put patients at risk. Drug therapy reduces this impairment, and AR patients should therefore be advised to always treat their condition.

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