Everything you want
to know about allergies

Advice and recommendations
for patients from EAACI experts

EAACI has developed this website to offer updated and reliable information on allergy to patients & families. Disclaimer

Allergens and triggers

Allergens are those substances that are able to induce an allergic response. They are outer substances that contact the organism through the respiratory or digestive systems or through the skin. Depending on the amount they are able to induce acute evident reactions. Every patient has his/her own threshold to respond with acute symptoms. An amount that is tolerated by a patient can cause a very severe reaction in others.

On the other hand, amounts of allergen under that threshold are able to cause a chronic underlying inflammation of the affected organs. This inflammation does not induce evident symptoms, but makes the organs hyperresponsive to many stimuli. The organ responds to those stimuli with evident symptoms, but the stimuli are not able to induce symptoms in organs without that previous inflammation. These stimuli are called triggers.

Thus, triggers are those factors that act on a previously inflamed organ and are able to cause an acute reaction They are easier to be identified and may distract attention on the cause of the underlying inflammation.

Allergens can act both as triggers and as a cause of inflammation.

Some triggers may also cause chronic inflammation, while others do not.

Here we describe the most frequent allergens and triggers