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allergens

allergens

introduction

  • allergen exposure in sensitive individuals may cause allergic rhinitis, conjunctivitis, pruritis and asthma
  • rarely, it may cause anaphylaxis
  • the main rule is to avoid allergens where possible, or at least minimise the exposure load
  • acute therapy of rhinitis/conjunctivitis is usually with antihistamines
  • if avoidance is not possible, systematic desensitisation may help

indoor aeroallergens

dust mites

  • the microscopic sized common household dust mites live in pillows, bedding, carpet, etc, particular in warm humid homes
  • their bodies and faeces are major sources of allergens which become aerodynamic particles 10 µm or larger in diameter and remain in undisturbed air for 30 minutes or less
  • the major sources of dust mite allergens are the group 1 allergens Der p 1 and Der f 1
  • levels of 10 mcg/g of dust induce allergic symptoms or asthma in sensitized persons, but lower levels may also cause symptoms in these individuals1)
  • ~25% of homes in USA have levels high enough to induce asthma
  • reducing exposure:
    • weekly vacuum cleaning
    • weekly washing of bedding in hot water
    • reduce indoor humidity
    • impermeable woven pillow and mattress covers
    • remove carpets and upholstered furniture

cat dander

  • 8-10% of the population are allergic to cats or will develop allergy if exposed to cats over a period of weeks
  • the major cat allergen is Felis domesticus (Fel d 1) which is produced by sebaceous glands and saliva and thus coats the cat's hair
  • of those with cat allergy, nearly 2/3rds have antibodies against Fel d 4 (a lipocalin), a product of the cat major urinary protein gene and which is secreted with saliva.
  • the allergen forms much smaller aerosolized particles (average size of 5 µm) than dust mites and readily coats walls and stays airborn in undisturbed air within a house for days!
  • recent studies suggest adults having a pet cat for the 1st time may be twice as likely to develop cat allergy
  • the proposed threshold level for sensitization by cat allergen is 1 mcg/g of dust, and the level to cause symptoms in susceptible individuals with asthma is 8 mcg/g of dust
  • the allergens may remain for months in the house even after removal of the cat
  • reducing cat allergy:
    • decrease your exposure:
      • ban the cat from being inside the house, or at least ban it from certain rooms such as bedrooms and close doors to prevent aerosols coming into the bedrooms
      • neutering male cats seems to decrease allergen secretion
      • shampoo cat weekly to reduce level of allergens on fur although most cats hate bathing and there may not be any evidence to support its benefits
      • brush hair regularly to remove and dispose loose hair
      • keep windows open as much as possible to ventilate the house
      • remove items that trap allergens such as carpets, rugs and pillows
      • clean regularly to remove dust using HEPA filters (have a non-allergic person do the vacuuming!), however, there is no evidence that vacuuming helps and the sweeping motion will disperse allergen into the air so choose a windy day with the windows and doors open.
      • wash hands frequently especially after touching the cat, and before touching your eyes, nose or mouth
      • don't forget your contaminated clothes will increase the load on your hands as well as take the allergen into your bedroom
    • treat symptoms:
    • systematic desensitisation can be useful for cat allergy and is designed to increase tolerance:
    • make sure it is the cat you are allergic to rather than the brand of cat litter, etc.

dog allergy

  • the major dog allergens, Canis familiaris 1 (Can f 1) and Canis familiaris 2 (Can f 2), have physical properties similar to those of cat allergens.
  • dogs should be washed twice a week if the owner is sensitive to them

cockroaches

  • only 5 of the 3500 known species are important indoor allergens
  • similar aerosol characteristics to dust mite allergens
  • may partly explain increased incidence of asthma in inner urban areas or substandard infested apartments

fungi

  • most of the fungi recovered from an indoor environment emanate from outside.
  • certain species, such as Penicillium and Aspergillus, can be found in greater quantities inside buildings and homes.
  • asthma severity has been linked to sensitivity to Alternaria species
allergens.txt · Last modified: 2012/04/20 20:08 (external edit)