About allergies
Allergies can impact anyone no matter their age, background or gender. Most allergic reactions are antibody-mediated and are also known as a type I hypersensitivity. An exception is allergic contact dermatitis which is cell-mediated and is a type IV delayed hypersensitivity reaction.
Type I hypersensitivity reactions starts when an allergen comes in to contact with the body and the immune system mistakes it for a foreign object that needs to be eradicated. In response the body’s B lymphocytes (a type of white blood cell) creates special antibodies known as immunoglobulin E (IgE) that circulate in the body and are specific for that allergen. When the body is exposed to the same allergen again, the IgE antibodies will recognise it and cause an immune reaction. Repeat exposure will increase the amount of IgE antibodies produced against the allergen and results in an allergy.
In allergic contact dermatitis a different white blood cell called T-lymphocytes migrate to the areas where the allergen is detected and cause the allergic reaction. Common allergens that trigger this are plants, cosmetics, perfumes, sunscreen, medicated creams and metals.
- Risks
- Symptoms
- Diagnosis & Treatment
General allergies
Some people can be genetically predisposed to developing allergies. This is called atopy and means they are more likely to be sensitive to allergens.
The incidence of allergies is higher in children as they tend to have a higher level of IgE in their system. The amount of IgE antibodies in their blood decreases from the age of 10. Children may also grow out of some of their food allergies such as egg and peanut allergies.
Environmental factors play an important part in allergy development. There are studies that indicate exposure of allergens such as food and pets to babies and infants may stop them from developing an allergy. There are also reports that contemplate whether an over-sterile environment can lead to children developing allergies easily later on due to under-development of their immune system.
Autosomal recessive hyper IgE syndrome
If both parents have AR-HIES they will pass it on to their child. People with autosomal recessive HIES generally have a shorter life span due to the many complications that can arise from this condition such as severe allergic reactions, infections and increased risk of cancer.
General allergies
Symptoms of an allergic reaction often depend on the type of allergen and can happen quickly or over a few hours. Allergens that are breathed in will cause symptoms in the respiratory tract and food allergens will affect the digestive tract and can also cause skin reactions. Common symptoms include:
- Itchy nose and eyes
- Runny, stuffy nose, sneezing
- Conjunctivitis
- Excessive swelling of the lips, mouth, throat, or at the site of an insect bite
- Skin rash such as hives or eczema
- Chest tightness or wheezing, difficulty breathing, cough, asthma.
For allergic contact dermatitis, the reaction can take a few days to occur. Common symptoms include:
- Skin rash that may be itchy
- Dry, scaly skin that may crack
- Swelling or burning skin
- Welts or blisters.
Anaphylaxis occurs when the person has an allergic reaction that is severe and only occurs during type I hypersensitivity. This happens very rapidly and can be life-threatening. Symptoms for anaphylaxis include:
- Drop in blood pressure leading to a weak and rapid heartbeat and light-headedness
- Unconsciousness
- Difficulty breathing
- Swelling of the throat
- Skin rash
- Nausea and vomiting.
Autosomal recessive hyper IgE syndrome
In AR-HIES, symptoms include:
- Eczema, skin infections, yeast infections
- Recurrent respiratory infections such as sinusitis, pneumonia
- Abscesses in lungs or skin
- Asthma and other allergic symptoms.
General allergies
Allergy testing combined with the symptom history can be done to find the type of allergen a person reacts to. The skin prick test is the most common where allergens are pricked into the person’s forearm or back with a needle. After 15-20 minutes each prick is checked for an allergic reaction. If a skin test is not possible, blood testing for allergen-specific IgE antibodies can be done but is not as sensitive.
Treatment involves reducing exposure to the offending allergen and medications to treat symptoms. Medications include:
- Antihistamines: block allergy irritants which reduces symptoms.
- Intranasal corticosteroid nasal sprays: used for hay fever, lowers swelling and mucous within the nose.
- Medical eye drops: used for itchy eyes and conjunctivitis.
- Adrenaline: used for anaphylaxis. Anyone at risk of having an anaphylactic reaction should carry an adrenaline injector.
Allergen immunotherapy involves giving increasingly larger doses of the allergen to eventually reduce the body’s immune response to the allergen.
Autosomal recessive hyper IgE syndrome
Diagnosis for autosomal recessive HIES involves genetic testing to detect relevant mutations and blood tests to determine the levels of IgE and various white blood cell levels. Treatments are often aimed at symptoms such as antifungal or antiseptic creams for skin rashes as well as antifungal or antibiotic aerosolised treatments for lung infections. A haematopoietic stem cell transplant (HSCT) or bone marrow transplant is considered to be a cure for AR-HEIS but may not completely resolve all immune issues.
This content is provided for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. If you have any concerns or questions about your health, please consult a suitably qualified healthcare professional.