What Is an Allergy?

An allergy is an abnormal reaction of a sensitive person to certain substances, like food or drugs, heat, or physical stimuli, that by themselves are not harmful. It includes production of IgE antibodies and release of histamine what results in typical allergic symptoms: itch, hives, wet eyes, sneezing, runny nose, cough, eczema or, in severe cases, short breath or fainting.

Above is description of the IgE allergy.

Can Allergy Cause a Headache?

Three types of a headache are often mentioned as related to allergy:

  • Sinus headache
  • Migraine
  • Cluster headache

A Sinus Headache

In people with dust allergy or hay fever, mucosa in sinuses (airy cavities in facial bones that are connected with nasal cavity) may get inflamed and swollen, thus obstructing connections among the sinuses and nasal cavity. Continuing mucus secretion increases pressure in the affected sinus, causing pain in cheeks, teeth, forehead, top of the head or elsewhere in the head.

It is a combination of facial pain, itchy wet eyes, runny nose, nose congestion, and sneezing that speaks for a sinus headache (allergic sinusitis).

Diagnosis of sinusitis may be confirmed by an X-ray. Diagnosis of an allergy is made by blood tests (elevated eosinophils and IgE antibodies) and skin tests.

Prevention is by avoiding dust and pollens.

Treatment is with antihistamines by mouth, intra-nasal corticosteroid sprays, decongestiants or immunotherapy.

Migraine

Migraine is a headache, usually appearing on one side of the head, accompanied by nausea, and sensitivity to light. It is due to abnormal dilation of vessels in head muscles and subsequent irritation of nearby nerves. It can be triggered by:

  • Specific light, sounds, or smells
  • Nutrients: amino acids such as tyramine (in cheeses), dopamine, phenylethylamine or monosodium glutamate (common additive in oriental and packaged foods), phenylethylamine (in chocolate), alcohol, or aspartame (artificial sweetener)

Above stimuli do not trigger production of IgE antibodies and histamine release, so they are non-allergic causes of migraine.

It was found out that people with food allergies or asthma often have migraines, but it is not clear how allergies and migraine are related. Antihistamines help to relieve symptoms in food allergies, but do not help in migraines that were supposedly caused by food.

A headache commonly appears in food intolerances, like celiac disease, fructose malabsorption, or hereditary fructose intolerance (HFI) , but these are not food allergies.

A Cluster Headache

A cluster headache is a sudden strong pain appearing in, behind, or around the eye, sometimes spreading to the face or head, usually only on one side only. It may last from 15 minutes to several hours. It often reappears in regular intervals, from here the term cluster (cluster = a group of resembling things, or events) and often at night, or in the morning, so it is also called an alarm-clock headache. Headaches may appear over the course of several weeks then disappear for some weeks, and another cluster of headaches may start.

Cluster headaches often occur in spring and autumn, so they were related with allergies (3), but this was not confirmed (4). Cluster headaches are associated with abnormalities in a part of the brain, called hypothalamus, and with abnormal vessel dilatation, like in migraine (5).

Related Articles:

References:

  1. Headaches caused by allergy (acaai.org)
  2. A sinus headache (allergies.about.com)
  3. A cluster headache (headaches.org)
  4. Do allergies cause a headache? (headaches.org)
  5. A cluster headache mechanism (emedicinehealth.com)

Article reviewed by Dr. Greg. Last updated on March 24, 2010