Migraine is not an allergy
Migraine is not an allergic disorder, but migraine is more common in people with allergies. Doctors noticed the link more than a century ago. Individual case reports dating mainly from the first half of the 20th century noted that allergies were common in migraineurs. This prompted theories that the allergic reactions triggered the migraine. The migraine disappeared when the allergy was treated, some studies claimed. From today's perspective, the research was not conclusive because of the short observation periods and typically very small number of cases studied.
Sniffing out the link: migraine and chronic rhinitis
More recent migraine studies looked at some of the complications of allergies, including chronic rhinitis (having a runny nose all the time) and asthma. A study into chronic rhinitis in 5894 migraineurs showed that impairment from headache events was worst in people with chronic rhinitis, either due to allergy or non-specific stimuli such as cigarette smoke, perfume, or the like.
The same subset of patients were also more likely to have asthma. The link between migraine and asthma was examined in more detail by a 2016 Taiwanese study in 127,798 subjects. The risk of migraine was found to be 1.45-fold higher in subjects with asthma.
A common but often incorrect diagnosis: "sinus headache"
It is an unfortunate fact that people with allergies are very often wrongly diagnosed with “sinus headache” when they actually have migraine. The Sinus, Allergy and Migraine Study (SAMS) by the Headache Center in Scottsdale, Arizona, showed as early as 2006 that a large proportion of patients with so-called sinus headaches were misdiagnosed.
Some of those cases were self-diagnosed but others were misdiagnosed by specialists. Of the total 100 subjects who believed they suffered from sinus headache, 52% actually suffered from migraine and 11% from medication-overuse headache associated with migraine. So overall, 63% of participants were affected by migraine. The mean time since the first headache was 24 years, and the current mean number of headache days per month was 14. The authors confirmed what others had suspected: sinus headache is the most common misdiagnosis in migraine patients.
Hope through allergy treatment?
A 2010 Medical University of Cincinnati study in 536 subjects investigating the effects of allergen-specific immunotherapy caused quite a stir when it showed that immunotherapy recipients had significantly less frequent and disabling migraine headaches than subjects not receiving immunotherapy – but only if they were under 40 years old.
Allergies are not the actual cause of migraine
None of the referenced studies sees the allergy as the cause of migraine, debunking the ‘allergy causes migraine’ theory. However, numerous studies do indicate that an allergy can be a major trigger for a migraine attack, especially if the allergen is breathed in and affects the mucous membranes of the head and neck.
One possible explanation is that an allergic reaction causes a burst in energy consumption and causes stress to the autonomic nervous system, which (like any kind of stress) can in turn trigger a migraine.
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References
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1. Martin VT, Fanning KM, Serrano D, Buse DC, Reed ML, Bernstein JA, Lipton RB. Chronic rhinitis and its association with headache frequency and disability in persons with migraine: results of the American Migraine Prevalence and Prevention (AMPP) Study. Cephalalgia. 2014 Apr;34(5):336–48. doi: 10.1177/0333102413512031. Epub 2013 Nov 25. PubMed PMID: 24275145.
2. Martin VT, Taylor F, Gebhardt B, Tomaszewski M, Ellison JS, Martin GV, Levin L, Al-Shaikh E, Nicolas J, Bernstein JA. Allergy and immunotherapy: are they related to migraine headache? Headache. 2011 Jan;51(1):8–20. doi: 10.1111/j.1526-4610.2010.01792.x. Epub 2010 Nov 4. PubMed PMID: 21054364.
3. Eross E, Dodick D, Eross M. The Sinus, Allergy and Migraine Study (SAMS). Headache. 2007 Feb;47(2):213–24. PubMed PMID: 17300361.
4. Peng YH, Chen KF, Kao CH, Chen HJ, Hsia TC, Chen CH, Liao WC. Risk of Migraine in Patients With Asthma: A Nationwide Cohort Study. Medicine (Baltimore). 2016 Mar;95(9):e2911. doi: 10.1097/MD.0000000000002911. PubMed PMID: 26945388; PubMed Central PMCID: PMC4782872.
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