1. House Dust Mites and Allergy
Jeffrey D. Miller MD
Assistant Clinical Professor of Pediatrics,
New York Medical College

2. Dr. Miller is the owner and CEO of Mission: Allergy, Inc.,
Disclosure:
Dr. Miller is the owner and CEO of
Mission: Allergy, Inc.,
a manufacturer and distributor of products for allergen-avoidance

3. House Dust Mites and Allergy
Anatomy and physiology of dust mites
Dust mites as allergen delivery systems
Dust mite allergen avoidance

4. House Dust Mites and Allergy
Anatomy and physiology of dust mites

5. Anatomy and physiology of dust mites
Dust mites are arachnids, not insects
--mites are microscopic relatives of spiders and ticks
--adult mites have 8 legs, not 6
Dust mites live near people (or other warm blooded animals), but not on them
Dust mites eat dead, shed human (and pet) skin scales. They do not bite.

6. Anatomy and physiology of dust mites
Adult dust mites are 250µ (= ¼ mm)
--the threshold of visibility
--easily seen under low power microscopy
Dust mites appear watery, not solid, under light microscopy
Electron microscope is only required to see fine detail

7. Anatomy and physiology of dust mites
D. pteronyssinus seen through electron microscope

8. Anatomy and physiology of dust mites
D. pteronyssinus seen through low-power light microscope

9. Anatomy and physiology of dust mites
Dust mites require at least 50% relative humidity to survive
--dust mites absorb water osmotically through specialized organs: “supra-coxal glands”
The ideal relative humidity for mites is 75%

10. Anatomy and physiology of dust mites
Supra-Coxal Glands

11. Anatomy and physiology of dust mites
Dust mites are light sensitive (although they have no eyes), and move away from the light
Dust mites are therefore not living on hard exposed surfaces, but rather borrowed into the dark recesses of soft materials:
pillows
mattresses
carpets
upholstered furniture
stuffed toys

12. Anatomy and physiology of dust mites
Dust mites live for about 80 days
A female dust mite lays about 60 eggs in her lifetime
The lifecycle includes:
Egg
Larva (6 legs)
1st stage nymph (“protonymph”)
2nd stage nymph (“tritonymph”)
adult

13. Anatomy and physiology of dust mites
Just as a lobster must molt its external skeleton in order to grow, dust mite larval and nymph stages must shed their external skeleton (“exoskeleton”) before growing into the next stage
These shed exoskeletons are a secondary source of mite allergen

14. Anatomy and physiology of dust mites
D. pteronyssinus seen through low-power light microscope
Note eggs (oval), nymphs (small), and shed exoskeletons (hollow)

15. Anatomy and physiology of dust mites
Electron-microscope view of dust mite egg
(with adhering fecal particles)

16. Anatomy and physiology of dust mites
Mites excrete solid waste particles
Mite waste particles are 25µ in size, the same size as pollen grains, and are easily inhaled
Digestion of nutrients continues outside of the mite’s body, due to a surrounding membrane containing digestive enzymes
Mites are coprophagic (eat their own feces), to gain additional digested nutrients

17. Anatomy and physiology of dust mites
Mite poop

18. Anatomy and physiology of dust mites
Close-up of mite poop

19. House Dust Mites and Allergy
Dust mites as allergen delivery systems

20. Dust mites as allergen delivery systems
Mite fecal waste particles are the primary source of mite allergens
Shed exoskeletons and debris from dead mites are secondary allergen sources

21. Dust mites as allergen delivery systems
The fecal particle’s weight and size are ideal for allergen delivery
Mite feces are 25µ, and are respirable
One mite can excrete 1000 of these particles during its 80 day life

22. Dust mites as allergen delivery systems
The fecal particle’s weight and size are such that they become airborne during disturbance, but settle within minutes
Mites waste particles become airborne when the material in which they are present is disturbed:
--making a bed
--putting one’s face on a pillow
--walking on carpet
--hugging a stuffed toy …etc.

23. Dust mites as allergen delivery systems
Many allergens occur in association with enzymes (pollens, molds, animal danders)
The digestive enzymes in the membrane surrounding the mite fecal particle aid in their reaching allergen-presenting cells, by digesting the “tight junction” between epithelial cells

24. Dust mites as allergen delivery systems
Mite feces are associated with substances, including bacterial DNA and endotoxin, that the body recognizes as belonging to primitive organisms, and which also elicit immune reactions

25. Dust mites as allergen delivery systems
Shed mite exoskeletons, and the body fragments of dead dust mites, are an additional source of mite allergens
Mite exoskeletons also contain chitin (also present in insects, shellfish, fungi, and intestinal worms), which also stimulates the immune system, producing chitinase enzymes

26. Dust mites as allergen delivery systems
Mite allergens can provoke symptoms by:
--contact (conjunctivitis, eczema)
--inhalation (rhinitis, asthma, eczema)
--ingestion (hives, anaphylaxis)

27. Dust mites as allergen delivery systems
Case report:
52 year-old dust-mite-allergic woman experienced her first episode of eye swelling and lip tingling shortly after eating pancakes made from a buttermilk pancake mix  that had been stored in a Rubbermaid container in her kitchen cabinet for several months.
Three months later, while cooking pancakes from the same mix, she experienced wheezing, diffuse redness, and facial swelling that again required emergency room care.

28. Dust mites as allergen delivery systems
Pancake mix seen through low-power light microscope

29. Dust mites as allergen delivery systems
Case report (continued):
On allergy evaluation she had positive prick skin tests to D. farinae and D. pteronyssinus (15mm wheal) and to the pancake mix (9 mm wheal). Prick skin tests to wheat were negative.

30. House Dust Mites and Allergy
Dust mite allergen avoidance

31. Dust mite allergen avoidance
Does allergen avoidance work?

32. Dust mite allergen avoidance
“If you don’t know where you are going, you might not get there!” --Yogi Berra

33. Dust mite allergen avoidance
“If you don’t ask the right question, you might not get the right answer” --me

34. Dust mite allergen avoidance
“Allergen avoidance” clearly works: -removing a pet from the home -quitting an occupational exposure -moving mite-allergic patients to high altitude

35. Dust mite allergen avoidance
The right question: “To what is the patient allergic; and what measures will decrease their exposure to their relevant allergens sufficiently to decrease their symptoms?”

36. Dust mite allergen avoidance
The right question: “To what is the patient allergic; and what measures will decrease their exposure to their relevant allergens sufficiently to decrease their symptoms?”

37. Dust mite allergen avoidance
The right question: “To what is the patient allergic; and what measures will decrease their exposure to their relevant allergens sufficiently to decrease their symptoms?”

38. Dust mite allergen avoidance

39. Dust mite allergen avoidance
Methods: 1122 adults with asthma, half given impermeable encasings, half given control (permeable) encasings
Results: “…there were no significant differences between …the active-intervention and control groups…”
Conclusion: “the use of allergen-impermeable bed covers as a single intervention for the avoidance of mite allergen seems clinically ineffective for the routine management of asthma in primary care.”

40. Dust mite allergen avoidance
In the press:
CNN – “Special bed covers bring no allergy, asthma relief”
Reuters Health – “If you're allergic to dust mites, using a mattress cover that blocks the bugs will probably not make you feel much better, findings from two new studies suggest.”
Associated Press – “Two studies found that mite-proof bed coverings, at least by themselves, fail to relieve asthma and allergies, a perplexing discovery that challenges the frequent advice of doctors.”
ABC News – “Dust-mite-proof bed covering, often recommended by doctors to help
asthma and allergy patients, aren't enough to stop sufferers from wheezing and sneezing, two new studies find.”

41. Dust mite allergen avoidance
BUT…
23% of patients were active smokers
An additional 22% of patients were former smokers
Patients were excluded if they did not require daily albuterol
55% of patients owned a cat or dog

42. Dust mite allergen avoidance

43. Dust mite allergen avoidance
Background: “Children with asthma who live in the inner city are exposed to multiple indoor allergens and environmental tobacco smoke in their homes”
Methods: 937 children with atopic asthma (age 5-11 years); randomized, controlled trial of environmental intervention that lasted one year and included education and remediation for exposure to both allergens and environmental tobacco smoke
Results: “The observed reduction in symptoms translates into 34 fewer days with reported wheeze...in the intervention group. This effect is similar to that described in placebo controlled studies of inhaled corticosteroids.”

44. Dust mite allergen avoidance
In the press:

45. Dust mite allergen avoidance
Cochrane Database Review 2008 Apr 16;(2):CD
House dust mite control measures for asthma.
Study: Meta-analysis of 54 studies of clinical effect of mite reduction measures in mite-sensitive asthmatics
Results: There were no statistically significant differences either in number of patients improved, asthma symptom scores, or in medication usage.
Author’s conclusions: Chemical and physical methods aimed at reducing exposure to house dust mite allergens cannot be recommended. It is doubtful whether further studies, similar to the ones in our review, are worthwhile.

46. Dust mite allergen avoidance
BUT…
Environmental control measures can only be expected to decrease symptoms if they succeed in decreasing allergen levels
Two thirds of the studies included in the Cochrane meta-analysis failed to lower allergen levels
Those studies that did lower allergen levels also lowered symptoms

47. Dust mite allergen avoidance
From Matthew Colloff, “Dust Mites”, Springer, 2009

48. Dust mite allergen avoidance
If it is a hard surface, WIPE If it is a washable fabric, hot water WASH If it cannot be wiped or washed, ENCASE If it cannot be wiped, washed, or encased, REMOVE If the indoor air is not dry, DEHUMIDIFY

49. Dust mite allergen avoidance
If it is a hard surface, WIPE If it is a washable fabric, hot water WASH If it cannot be wiped or washed, ENCASE If it cannot be wiped, washed, or encased, REMOVE If the indoor air is not dry, DEHUMIDIFY

50. Dust mite allergen avoidance
If it is a hard surface, WIPE If it is a washable fabric, hot water WASH If it cannot be wiped or washed, ENCASE If it cannot be wiped, washed, or encased, REMOVE If the indoor air is not dry, DEHUMIDIFY

51. Dust mite allergen avoidance
If it is a hard surface, WIPE If it is a washable fabric, hot water WASH If it cannot be wiped or washed, ENCASE If it cannot be wiped, washed, or encased, REMOVE If the indoor air is not dry, DEHUMIDIFY

52. Dust mite allergen avoidance
If it is a hard surface, WIPE If it is a washable fabric, hot water WASH If it cannot be wiped or washed, ENCASE If it cannot be wiped, washed, or encased, REMOVE If the indoor air is not dry, DEHUMIDIFY

53. Dust mite allergen avoidance
If it is a hard surface, WIPE If it is a washable fabric, hot water WASH If it cannot be wiped or washed, ENCASE If it cannot be wiped, washed, or encased, REMOVE If the indoor air is not dry, DEHUMIDIFY

54. Dust mite allergen avoidance
If it is a hard surface, WIPE
Dust mites are not living (or producing allergen) on hard, wipe-able surfaces
Allergen on those surfaces was produced elsewhere, and has settled there
Use a microfiber dust cloth or Swiffer® to trap dust, rather than just redistributing it
The more wipe-able the room, the better

55. Dust mite allergen avoidance
If it is a washable fabric, hot water WASH
Wash all bedding, including blankets, every 1-2 weeks (unless allergen-barrier comforters)
Water need not be 130o
130o is the temperature that will scald mites to death—but we don’t care if they are scalded, drowned, or washed down the drain
Even cold water will remove 90% of mites
Water at 130o is a potential hazard to children

56. Dust mite allergen avoidance
If it is a washable fabric, hot water WASH
Water need not be 130o
Warm water will remove 98% of the mites
Ten minutes in a clothes dryer will kill all mites
A trick: dry clothing for 10 minutes first; then wash, even in cold water

57. Dust mite allergen avoidance
If it cannot be wiped or washed, ENCASE
Encase pillows, mattress and box spring in allergen-impermeable covers
Alternatively, replace existing pillows with new pillows made with allergen-barrier outer fabric
Encase all pillows on the bed
As an alternative to washing, comforters may be encased, or replaced with allergen-barrier comforters

58. Dust mite allergen avoidance
If it cannot be wiped or washed, ENCASE
Encasing types:
Vinyl (very uncomfortable)
Urethane laminate (somewhat uncomfortable)
Microfiber (allow air, heat and vapor passage)
Woven microfiber--best, if sufficiently tight
Non-woven microfiber (feel like a thick paper towel)--allow mite colonization and allergen accumulation!!

59. Dust mite allergen avoidance
If it cannot be wiped or washed, ENCASE
Woven Encasing Non-woven Encasing

60. Dust mite allergen avoidance
If it cannot be wiped or washed, ENCASE
Woven Microfiber—light microscope view

61. Dust mite allergen avoidance
If it cannot be wiped or washed, ENCASE
Woven Microfiber—electron microscope view

62. Dust mite allergen avoidance
If it cannot be wiped or washed, ENCASE
Non-Woven Microfiber—light microscope view

63. Dust mite allergen avoidance
If it cannot be wiped or washed, ENCASE
Mites on WOVEN encasing—stay on surface

64. Dust mite allergen avoidance
If it cannot be wiped or washed, ENCASE
Mites on NON-WOVEN encasing—burrow into fabric

65. Dust mite allergen avoidance
If it cannot be wiped or washed, ENCASE
Encasing types:
Microfiber (allow air, heat and vapor passage)
Non-woven microfiber (feel like a thick paper towel)--allow mite colonization and allergen accumulation! AVOID!
Woven microfiber--best, if sufficiently tight

66. Dust mite allergen avoidance
If it cannot be wiped or washed, ENCASE
All woven microfibers are not equal.
They vary in the number and size of their pores.
Very tightly woven microfiber fabric Less tightly woven microfiber fabric

67. Dust mite allergen avoidance
If it cannot be wiped, washed, or encased, REMOVE
If possible, remove the bedroom carpet, leaving hardwood, tile or linoleum flooring
washable throw rugs are OK, if washed regularly
Remove
stuffed toys
throw pillows
upholstered furniture (use wood, plastic, leather)
pennants
curtains …etc.

68. Dust mite allergen avoidance
If the indoor air is not dry, DEHUMIDIFY
Keep humidity below 50%, if possible
obtain a humidity gauge
use air-conditioner , dehumidifier in summer
avoid winter humidifier use, or use sparingly
Even lesser decreases in humidity (below 75%) are helpful, as they decrease dust mite growth and allergen production somewhat
less mite growth →less mite feces

69. Dust mite allergen avoidance
If it is a hard surface, WIPE If it is a washable fabric, hot water WASH If it cannot be wiped or washed, ENCASE If it cannot be wiped, washed, or encased, REMOVE If the indoor air is not dry, DEHUMIDIFY

70. Dust mite allergen avoidance
Do I have to do everything?

71. Dust mite allergen avoidance
“ A chain is as strong as its
weakest link”
“ If can can, if no can no can”
--Hawaiian saying

72. Warning: paying too much attention to dust mites
can lead to everything looking like a dust mite