Allergy

types of allergy

1. ALLERGY EMANI APARNA SRINIVAS COLLEGE OF PHARMACY

2. Allergy Allergy is defined as “the abnormal or unusual response to a substance by human body is called allergy. OR The harmful reaction to the external substances is known as allergy. The external substances are known as allergens.

3. Allergens These are antigenic substances capable of sensitizing the body in such a way that unusual responses occur in the hypersensitivity individuals. Almost any substances whether its biological, chemical or synthetic origin, may prove to be allergens.

4. Mechanism of action of allergens Generally allergic reactions takes place in following steps Primary Exposure Secondary Exposure & Release of mediators

5. Primary Exposure: When the body is first subjected to the allergen (antigen), the condition is referred to as primary exposure. Because no antibodies has been formed previously, no symptoms of the allergy are produced during the primary exposure.

6. Secondary Exposure and release of mediators However during the subsequent exposure, the allergen contacts the antigen-antibody reactions. During secondary expose the antibody become attach to the mast cells-white blood cells (basophils), and form a complex and as a result basophils burst due to antigen-antibody reaction causes a liberation of histamine, bradykinin and other mediators of allergic symptoms.

7. Types of Allergens Inhalant Allergens: Substances that are distributed in the atmosphere and contact the nasal or buccal mucosa during respiration are called inhalant allergens. Ingestant Allergens: Those that occur in the foodstuff and are swallowed are known as ingestant . Injectants Allergens: Those may be present in the solutions intended for parenteral administration are known as injectants .

8. Food allergy Food allergy is a specific form of hypersensitivity of food that activates the immune system, leading to an exaggerated response. An allergic response is usually triggered by a small amount of food proteins. In a true allergic reaction, the immune system produces antibodies. The class of antibodies known as IgE reacts with the antigen and this in turn triggers a reaction with the mast cells and basophils .

9. Mast cells are found below the surface of the skin, respiratory tract, eyes. A substance called histamine and other substances such prostaglandins and leukotriene are released from mast cells and they cause allergic response.

10. Examples Milk Allergy: Milk allergy is a specific immunologic, antigen-antibody response owing partially to lactalbumin. This protein acts as allergen and responsible for antigen-antibody reaction. Because on heating or boiling alter this protein and thus no antigenicity .

11. Symptoms of food allergy Milk allergy may result in Severe dermatitis Recurrent Rhinorrhea Bronchitis Asthma Various commercially milk substitutes that are prepared from soybean isolates offer a milk-free formula claimed to be devoid antigenicity .

12. Coffee Allergy: It has been determined that coffee can produce allergic response. Symptoms of Allergy: Severe migraine, gastroenteritis and widespread hives Causes: The principal water-extractable allergenic component of green coffee is chlorogenic acid (3-caffeoylquinic acid).

13. Treatment: the main treatment of this type of allergy is to remove that material from food, which cause allergy or hypersensitivity reactions. All the allergens are available in the form of extracts, which are obtained from food. These allergens are injected to the hypersensitive person, if he response, he will avoid to take this food.

14. Drug allergy For most of the patients having allergies, medicines are used to begin therapy, for example. Most forms of hay fever are easily controlled with antihistamine drugs. The antihistamine only prevent the release of histamine. These could not prevent the antigen antibodies reactions. Antihistamine relieves symptoms such as itching, and sneezing produced by histamine.

15. Some of the distinct clinical symptoms of drug allergy includes the following: Serum sickness: The reaction typically occurs 7 to 10 days after exposure and causes fever and rash. Mechanism: drug-antibody complexes and complement activation. Some patients have oedema or GI symptoms .

16. 2. Hemolytic anaemia : Antibody-drug-RBC interaction occurs. Eg: methyldopa alters the RBC membrane uncovering an antigen that induces autoantibody production. 3. Pulmonary effects: Some drugs induce respiratory symptoms, deterioration in pulmonary function and other pulmonary changes. 4. Renal effects: Tubulointerstitial nephritis is the common allergic renal reaction. Methicillin , antimicrobial and cemitidine .

17. CHEMICAL ALLERGIES Chemical allergy is an adverse reaction to a chemical resulting from previous sensitization to that chemical or to one that is structurally similar. A chemical allergy is initiated by the immune system and expressed as a hypersensitivity reaction after an initial allergic reaction to a chemical, a very small subsequent exposures can evoke a severe response.

18. Example 1: Polyisocyanates induce hypersensitivity response and are responsible for lung disease among industrial workers. Used in the manufacture of adhesives, paint hardeners, elastomers and coatings.

19. Example 2: Acid anhydrides used in the production of paints, varnishes, coating materials, adhesives, casting and sealing materials can elicit hypersensitivity reactions. Asthma, anemia, contact dermatitis hypersensitivity pneumonitis.

20. Example 3 Metals can evoke contact and pulmonary hypersensitivity responses. Nickel is a common contact sensitizer upon prolonged exposure, common through jewellery , coins and clothing fasteners.

21. Example 4: Beryllium can produce contact and tuberculin type of hypersensitivity. Exposure occurs- aerospace, high ceramic manufacturing, electronics, nuclear weapons and reactor industries

22. Example 5: Cosmetics Personal hygiene products Enzyme extract from plants can elicit hypersensitivity reactions.