The most common allergic diseases are rhinitis or allergic conjunctivitis, affecting one out of every five people worldwide, and are frequently associated to asthma.

Depending on the type of allergen and the port of entry, the following different conditions can be found:

• Conjunctivitis: itchy eyes, watery eyes, sensation of burning or fine sand in the eye, reddening of eyes.
• Rhinitis: nasal itching, continual sneezing, nasal obstruction, nasal drip or rhinorrhoea, sensation of stuffy nose.
• Allergic asthma: cough with or without expectoration, suffocation, wheezing, difficulty breathing.
• Atopic dermatitis: rash located on skin folds, frequently in children.
• Urticaria: swelling or wheals, itching or skin rash.
• Angioedema: swelling of eyelids, lips or limbs. When oedema is located on the tongue or the larynx (oedema of the glottis), it is a medical emergency due to risk of asphyxia.
• Contact dermatitis: rash on the areas of skin that came into contact with the allergen.
• Anaphylaxis: certain insects, medicinal products and some foods may trigger all the abovementioned symptoms aggravated by hypotension, vomiting, diarrhoea and cramps, which may be life threatening.