Allergy is the altered capacity of body to react to a foreign substance. Allergy is caused by certain biological and abiological agents present in the atmosphere. The allergy causing agents present in air are called aeroallergens, and the allergy caused by them is called aeroallergy. Some of the prominent aeroallergens are house dusts, pollen grains, cosmetics, microbial spores or cells, etc. There are four types of allergic reactions-
a. IgE-dependent,
b. Cytotoxic tissue specific antibody,
c. Toxic antigen- antibody complexes with activated complement,
d. T- lymphocyte cell mediated hypersensitivity.

House dust is a mixture of hair, moulds, bacteria, decomposed part of cloths or furniture, small insects, mites, etc. These are inhaled by the individuals. The most common fungal spores isolated from the allergic individuals are the species of Aspergillus, Rhizopus, Cladosporium, Curvularia, Helminthosporium, Phoma, Fusarium, Cephalosporium, Nigrospora, Epicoccum, Penicillium, etc.

Mites are the important component of house dust and strong allergens for humans. Some mites are Drematophagoides farina, D. gallinae (poultry mite), D. domesticus, D. destructor, D. pteronyssinus, etc. D. ptreonyssinus is found in large number on mattresses, blankets, pillows, etc where human scales are abundant. These are distributed in all houses equally.

D. pteronyssinus is commonly known as house dust mite which dominate by 88% almost in all houses. Children shed considerable amount of skin in house, which serve as a culture medium to D. pteronyssinus. Human skin is a good source of nutrients in the house dust. It is proved that the dead mites and their different body parts, faeces and secretions are equally potent allergens as the live mites. The housewives, domestic cleaners and decorators are found to be victimized by house dust mite. Mite faeces are the major source of house dust allergens. They are related to the presence of mites and the 95% of the allergens accumulating in mite cultures were associated with faecal particles.

Aeroallergens are of different types in different regions and places. After attaining maturity the pollen grains get disseminated and dispersed through vectors like wind, water and insects. Occurrence and abundance of pollen grains in the environment differ according to season and vegetation types. Allergic potentials of pollen grains is governed by their chemical constituents.

Cosmetics are the articles which are used by us to beautify or promote attractiveness in our personality. The examples of cosmetics of daily use are creams, gels, powders, lotions, perfumery items, oils, dyes, lipsticks, bindi, eye cosmetics etc. These cosmetics show dermatological problems. The causes of allergies are:
a. The quality products of cosmetics,
b. Spoilage of cosmetics by microorganisms (E. coli, Aerobacter, Bacillus subtilis, Alternaria, Aspergillus, Cladosporium, Fusarium, Candida, Torula, Trichoderma, et.
c. Secretion of toxins by microorganisms,
d. Chemical ingredients of cosmetics,
e. Inadequate preservative system,
f. Packaging materials , and
g. Mode of use.

Hair dyes are the most common cause of contact dermatitis among the cosmetics. The paraphenylenediamine present in hair dyes is the most common sensitizer. Dyes used for colour causes dermatitis, eosin is a potent photocontact sensitizer. Adhesive material of bindi contains 70-80% paratertiary- butyl phenol which is a causal factor of contact dermatitis and other skin allergies after constant use of bindis. Foaming agent is known to be chief cause of contact dermatitis. Barium sulphide in hairs creams/ lotions is a strong cauterizing agent for the skin. It can damage the skin if left blank in contact for a long time. Hair oils and shampoos are also proved to be harmful.

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