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

List of symptoms

The symptoms caused by allergy can be considered as defence mechanisms to protect our organism from allergens. The symptoms also act as an alarm, warning us that something is wrong. But these defence mechanisms can become harmful to ourselves. People who don't suffer from allergies have other defence mechanisms that do not harm them, and thus allergens go unnoticed.

The most frequent symptoms associated to allergic disorders are shown here in alphabetical order. You can check them by the organ involved with our Allergy Body Guide.

IMPORTANT TO NOTE: None of these symptoms are exclusive of allergy. Any of them can be caused by other conditions, some of them very serious. The symptoms are shown here for information, but if you suffer from them we recommend you to visit a doctor.

 abdominal pain

Abdominal pain

A pain in the stomach area, often associated to vomiting or diarrhoea, appears when the digestive system if not correctly functioning. When the pain is colicky it is due to the accelerated movement of the bowels trying to expel their contents as fast as possible. This is associated to allergic disorders such as food allergy, hereditary angioedema and anaphylaxis.

 heartburn

Chest tightness

Sensation of pressure on the chest, it causes difficulty in breathing. It appears when we try to expand our chest to let air come in. If the airways are narrowed and the air cannot pass easily you will feel this sensation. This is associated to allergic disorders such as asthma or anaphylaxis.

 cough

Cough

When we cough, we expel air from the lungs forcefully, which helps to clear the airways from secretions, irritants, and foreign particles such as allergens and microbes. This is associated to allergic disorders such as asthma, rhinitis, rhinosinusitis, hay fever and anaphylaxis.

 diarrhea

Diarrhoea

Discharge of loose or liquid stools, when a food has not been digested, or due to an accelerated transit of the food in the bowels, to expel something that the organism does not admit. This is associated to allergic disorders such as food allergy and anaphylaxis.

 breathe

Difficulty breathing, shortness of breath, breathlessness, or dyspnoea

The feeling of difficulty in inhaling or exhaling air appears when we try to breathe through a narrowed airway. It is a warning signal, and if not reverted, it can lead to exhaustion of the respiratory muscles. You can have this feeling if you try to breathe through a straw. This is associated to allergic disorders such as asthma and anaphylaxis.

 swallowing 3

Difficulty swallowing

A feeling of pain or discomfort when swallowing, or even the sensation that the food is stuck, can appear once the food passes through a constricted and rigid oesophagus, due to the infiltration of inflammatory cells. This is associated to allergic disorders such as eosinophilic esofagitis.

 dizzy1

Dizziness

Dizziness means an impairment in spatial perception and stability. It can appear due to a drop in blood pressure - called shock - when it is extreme. This is associated to allergic disorders such as anaphylaxis.

 eyebags1

Eye circles

The blood coming from the eyes and going to the heart passes through the veins in the nose. If these are congested due to inflammation of the nasal mucosa, eye circles appear. This is associated to allergic disorders such as rhinitis, hay fever, conjunctivitis and anaphylaxis.

 eyeitching1

Eye itching

Due to infiltration of cells in the nasal mucosa it is an alarm warning that something is going wrong in our eyes. This is associated to allergic disorders such as conjunctivitis and anaphylaxis.

 redeye

Eye redness

Due to the dilation of blood vessels in the surface of the eyeballs, these appear red. This is associated to allergic disorders such as conjunctivitis and anaphylaxis.

 headache

Headache

Among many other causes, headache can occur due to nasal congestion or to the blockage of the mucus secretion in the sinuses - cavities within the bones of the head. This is associated to allergic disorders such as rhinitis, hay fever and rhinosinusitis.

 chest pain1

Heartburn

This burning sensation beneath the breastbone can appear when the acid content of the stomach is moved backward to the oesophagus, due to a malfunctioning of the junction between the oesophagus and the stomach. This is associated to allergic disorders such as eosinophilic esofagitis.

 smell

Loss of smell

The loss of the sense of smell is due to a malfunctioning of the nose when there is an infiltration of the nasal mucosa or an abnormal growth of tissue, forming polyps. This is associated to allergic disorders such as rhinitis, hay fever and nasal polyposis.

 nasalblockage1

Nasal blockage

The blocking of the passage of air through the nose can happen when there is an obstruction due to mucus secretion, to the inflammation of the nose, to the hypertrophy of the bones inside the nose called turbinates, or to the growth of tissue inside the nose, forming polyps. This is associated to allergic disorders such as rhinitis, hay fever, nasal polyposis and anaphylaxis.

 nausea1

Nausea

This sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit commonly precedes vomiting, which is a defence mechanism to get rid of content in the stomach that has been identified as harmful by our organism. This is associated to allergic disorders such as food allergy and anaphylaxis.

 nosebleed

Nose bleeding

Bleeding from the nose can happen when the nasal mucosa is infiltrated and thus congested with blood vessels and very fragile. This is associated to allergic disorders such as rhinitis, hay fever and nasal polyposis.

 noseitch

Nose itching

Due to infiltration of cells in the nasal mucosa it is an alarm warning that something is wrong in our nose. This is associated to allergic disorders such as rhinitis, hay fever and anaphylaxis.

 nosemucus

Nose mucus

Either liquid or thick, transparent or coloured, mucus in the nose has the objective of catching and neutralising stimuli identified as harmful. This is associated to allergic disorders such as rhinitis, hay fever and anaphylaxis.

 itching

Skin itching

The sensation that causes the desire or reflex to scratch appears due to the stimulation of skin receptors and may act as a signal that something is wrong. This is associated to allergic disorders such as atopic dermatitis, contact dermatitis, urticaria and anaphylaxis.

 skinredness

Skin redness, dryness, desquamation or skin peeling

These appear when the blood vessels are dilated due to harmful stimuli, when the protecting fatty layer of the skin is not repaired, and when the normal cycle of renewal of the skin is impaired. These are associated to allergic disorders such as atopic dermatitis or contact dermatitis.

 sneeze

Sneezing

This sudden loud expulsion of air from the lungs through the nose and mouth helps clearing the airways from substances identified as harmful. This is associated to allergic disorders such as rhinitis, hay fever and anaphylaxis.

 swollen

Swelling, oedema, or inflammation of the skin

This is due to the drip of liquid from the blood vessels to the deeper layers of the skin. This is associated to allergic disorders such as urticaria, anaphylaxis and hereditary angioedema.

 swolleneyelid

Swollen eyelids

They appear due to the drip of liquid from the blood vessels to the skin, due to a local congestion or to a generalised reaction. This is associated to allergic disorders such as rhinitis, hay fever, conjunctivitis, anaphylaxis and hereditary angioedema.

 swollenface1

Swollen face

It appears due to the drip of liquid from the blood vessels to the skin, due to a local or a generalised reaction. This is associated to allergic disorders such as urticaria, anaphylaxis and hereditary angioedema.

 tearing1

Tearing

The secretion of tears helps clearing the eyes from foreign substances; at the same time some components in tears neutralise these substances. This is associated to allergic disorders such as conjunctivitis and anaphylaxis.

vomiting

Vomiting

The involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose has the objective of getting rid of content that the organism identifies as harmful. This is associated to allergic disorders such as food allergy and anaphylaxis.

hives

Weals,  or hives.

They are pale red, raised, itchy bumps in the skin, due to the drip of liquid from the blood vessels to the superficial layers of the skin. They are associated to allergic disorders such as urticaria and anaphylaxis.

wheezing1

Wheeze


Wheezing is a whistling sound produced during breathing, when the air passes through a narrowed or obstructed airway. It can happen in bronchospasm, when bronchi contract trying to prevent the passage of harmful stimuli, but at the same time, this constriction impairs the passage of air. This is associated to allergic disorders such as asthma or anaphylaxis.