Some people experience headache as a symptom of an allergic reaction. The American College of Allergy, Asthma and Immunology (ACAAI) points out that allergies do not cause most headaches, but in cases where headache symptoms occur during an allergic reaction, symptoms may fall into one of three categories: migraine headache, cluster headache or sinus headache.
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A person who experiences a migraine as a symptom of an allergic reaction will begin to feel throbbing pain, often on only one side of the head. The level of pain ranges from dull or moderate to severe. Some symptoms of migraine are identical to other symptoms of allergic reactions, such as nausea and vomiting. Other migraine symptoms do not usually occur as symptoms of an allergic reaction. These migraine-related symptoms include sensitivity to sound or light, increased urination, fatigue, numbness, weakness and chills. The American College of Physicians notes that migraines may last up to three days.
A person having an allergic reaction may experience a severe form of headache known as a cluster headache. Symptoms include a sudden onset and extreme pain on one side of the head. The pain may strike around or behind one eye, and usually reaches peak intensity within 10 minutes. The pain may continue at that level for up to three hours, and the person's nose may become red and swollen. The affected eye may also become red and swollen, and may tear up. Some symptoms of cluster headache not usually associated with allergic reactions by themselves include sensitivity to smell, sound or light, and restlessness or agitation.
Health professionals at the ACAAI uses the term "sinus headache" to describe facial pain associated with swollen and blocked sinuses, and they include this as a possible allergy headache symptom. When the sinuses cannot drain into the nasal passages, pressure builds up in these cavities, which lie in the forehead and cheekbones and behind the eyes and the bridge of the nose. This pressure can cause pain in the top of the head or in the cheeks, jaw or teeth.