Dealing with dust mites

I developed dust mite allergies relatively late in life (late 20s). Partly because I developed them as an adult, I’ve been much less willing than other allergics I know to accept my symptoms as a given, and so I’ve collected an unusual amount of information about how to ameliorate dust mite allergies. That information follows.

If you don’t want to read this whole thing, the suggestion you’re least likely to find elsewhere is to put a dehumidifier set to 45% RH in the closet you store your clothing and sheets in.

If you do read this whole thing and have questions or suggestions for additional tips, please reach out. As you can tell, I’m desperate.

Facts about dust mites

I’ll get to the tips and tricks in a second, but first it’ll be helpful to know some things about dust mites and the allergens they produce. Unfortunately, I’ve lost my reference to the paper that I distilled this information from, so you’ll have to take it on faith :)

1. Dust mites are microscopic arthropods that consume microorganisms and shed human skin.

2. Dust mite allergies are triggered by proteins in mite carcasses and mite feces.

3. Dust mites are well-adapted to environments that are suitable for humans, and especially thrive in warm, humid environments.

4. At 72F and 70% relative humidity (RH), dust mite populations grow enough to trigger (my) allergy symptoms within 2-3 days.

5. Dust mites don't grow well below 50% RH.

6. Dust mites can survive continuously low humidity for weeks, can survive low humidity indefinitely with as little as 1.5 hr/d of elevated humidity, and can reproduce with as little as 3 hr/d of elevated humidity.

7. Porous materials that come into extended contact with humans, like clothing, bedding, and upholstered furniture, are microenvironments with mite food sources (shed skin) and elevated humidity relative to the ambient environment.

8. Porous materials with pore size smaller than 10 μm block the passage of dust mite allergens.

9. Dust mite allergens readily become airborne with disturbances, but settle within 15 minutes.

10. Dust mite allergens are removed from fabric by standard detergents by hot- but not cold-water laundering.

11. Benzyl benzoate (Acaryl) and Allersearch's proprietary ADMS can be added to cold-water wash to remove mite allergens.

12. Tea tree, eucalyptus, and cinnamon essential oils, and tannic acid repel and kill dust mites.

13. Some people (me) with dust mite allergies experience cross-reactions to the following triggers. This is not intended to be an exhaustive list.

    1. Other arthropods, most notably crustaceans.

    2. Mite-contaminated flour. This is known as oral mite anaphylaxis or, colloquially, pancake syndrome.

    3. Salicylates, especially in asprin and spices. This is known as salicylate sensitivity, or sometimes aspirin-exacerbated respiratory disease (AERD).

Taken together, these paint a picture where, except in arid climates, dust mites are ubiquitous and their allergens are especially concentrated in bedding, clothing, upholstery, and carpeting. Because allergens produced by dust mites persist if dust mites leave (and are generated when they die), effective strategies for allergen abatement emphasize preventing dust mite growth. However, because of their ubiquity, some amount of allergen removal is typically required.

Techniques for managing allergies

The following is a list of strategies to reduce exposure and response to dust mite allergens, ordered from 'change the environment' to 'change yourself'. Unless you're willing to move to the Rockies, you'll realistically have take action down the list.

Some of these are elaborated after this list; most are not. If there’s any that you’d like more detail on, reach out and I’ll write it up.

1. Prevent dust mite growth

   1. Live in a dry environment

   2. Store fabrics in a dehumidified closet

   3. Use insect repellants/acaricidals (cautiously)

2. Elimiate habitable environments

   1. Replace fabric with non-porous alternatives where possible

   2. Use mite-unfriendly fabrics where necessary

   3. Replace carpets with hard surface flooring

   4. Avoid exposed brick, unfinished wood, and other rough surfaces

3. Remove dust mite allergens

   1. Launder clothing and bedding frequently with an anti-allegen detergent

   2. Vacuum, mop, and dust frequently

4. Occlude dust mite allergens

   1. Encase bedding in small pore-size covers

   2. Wear a mask (/ respirator)

   3. Use a filtered CPAP machine

5. Ameliorate symptoms

   1. Reduce inflammation

   2. Take antihistamines (intermittently)

6. Try immunotherapy

Live in a dry environment

Controlling relative humidity is the most straightforward way to prevent dust mite growth: if the humidity is continuously below 50%, dust mites won't grow. The simplest way to achieve this is to live in a desert or at high altitude.

At baseline, the absolute humidity indoors matches the absolute humidity outdoors, and the relative humidity is determined by that absolute humidity and the indoor temperature. Various activities perturb the indoor humidity, e.g. showering and cooking raise it; traditional AC (ie not evaporative cooling) lowers it.

The relationship between temperature, absolute humidity (I'll use "dew point" interchangeably), and relative humidity is non-linear, but one data point to keep in mind is that the relative humidity is 50% at a temperature of 70F and a dew point of 50F. As the absolute humidity increases, the relative humidity increases; as the temperature increases, the relative humidity decreases.

To give a sense for which cities support this strategy: Colorado is well known for not supporting dust mite growth. US East coast cities are especially bad during the summer. San Francisco is known to be bad for dust mite allergy sufferers, in part because its poorly-insulated houses run cold, which increases the relative humidity.

If you’re curious about seasonal dew point variation in your location, find a weather station near you on the Weather Underground and look at the history for that station. If you're curious about whether a particular combination of dew point and indoor temperature will support dust mite growth, you can use this dew point calculator.

A word of caution: places that are dry enough to entirely preempt dust mite growth are also dry enough for efficient household cooling via evaporative ("swamp") coolers. These increase indoor humidity enough to moot the benefit of living in a dry environment.

Store fabrics in a dehumidified closet

Even if ambient indoor humidity can't be kept low enough to prevent dust mite growth, it's often still possible to create pockets of low humidity to store particularly dust mite-sensitive objects, especially bedding and clothing.

Closets with hinged, single-piece doors make ideal spaces for this: with a little weather stripping, low capacity dehumidifiers are enough to keep the space sufficiently dry. I use a combination of silicone door seal and rubber weatherseal tape, and a 22 pint dehumidifer. This dehumidifier comparison chart may be helpful.

The reason this technique makes such a big difference is that, in humid conditions, dust mites grow even in fabric that hasn't been used since laundering, and can produce enough allergens to trigger a response within a few days. Keeping a dehumidified closet allows you to delay the starting of that countdown until you're ready to put the sheets on your bed (or clothing on your body) without having to launder on immediately before changing them.

I don't recommend applying this dehumidifier approach to entire households, because it's just too hard to maintain humidity differentials between indoors and ourdoors. This has been formally tried and results were underwhelming (I lost the link to this paper, too).

Use insect repellants/acaricidals (cautiously)

I mentioned six substances that repel and/or kill dust mites: tea tree oil, eucalyptus oil, cinnamon oil, tannic acid, benzyl benzoate, and Allersearch’s ADMS.

Unfortunately, all six of these are respiratory irritants (and tannic acid turns things brown). Benzyl benzoate in particular is noxious and not recommended. My sense from unrigorous experimentation is that the Allersearch formulations work as advertised and are less irritating than the other options on the list.

Replace fabric with non-porous alternatives where possible

Some suggestions:

• Wood flooring instead of carpet

• Waxed cotton, leather, or synthetic material for outerwear

• Leather or synthetic material for couches

• Wood or plastic for blinds, instead of curtains

Use mite-unfriendly fabrics

In order to qualify as mite-unfriendly, fabric must (1) have a small pore size and (2) be amenable to frequent washing. It’s difficult to get pore size estimates for fabrics; a good proxy to use is water resistance. Random notes about specific fabrics:

• Technical clothing is often a good choice.

• Of common yardage fabrics, ticking fabric is the most tightly-woven, followed by percale.

• Wool is often billed as mite-unfriendly, because some properties of the fibers slow dust mite growth, but the fact that most wools shouldn’t be washed frequently in a machine has taken it out of my wardrobe.

• Denim is, unfortunately, very mite-friendly.

Vacuum, mop, and dust frequently

This type of cleaning is, annoyingly, important to do on a regular basis to keep allergen load low.

I don’t recommend robot vacuum cleaners: the side brushes they use to move debris into the path of the vacuum kick a lot of dust up, and the whole robot inevitably becomes toxic with dust. My current strategy is to use a HEPA vacuum with a large enough dust bin that it’s not a big deal to ask a friend without allergies to empty it very, very occasionally.

I’ve gone through a few mops in the past few years, and I’ve found this youtuber’s recommendations (in the description of the linked video) agreeable. Using disposable microfiber mop pads does feel a bit wasteful, though.

Encase bedding in small pore-size covers

This includes mattress encasement, pillow encasement, and comforter encasements. Mattress and pillow encasements marketed specifically for allergy sufferers are common, but I’ve had more trouble sourcing the comforter encasements recently. The company I used to purchase from, National Allergy, seemed to start having some issue with their stock. The best option here may be to purchase cotton ticking (or maybe percale) fabric yourself and sew it into comforter encasement.

Reduce inflammation

The challenge here is that allergen exposure worsens systemic inflammatory status, and systemic inflammation worsense allergy symptoms.

Look, it’s well understood that diet and lifestyle have a large effect on inflammatory status. I’m not going to recommend a specific approach to diet, because that seems to be the most reliable incantation to summon angry internet hordes (or maybe that’s how to get this blog to go viral??)

Take antihistamines (intermittently)

Antihistamines can be helpful for relieving upper respiratory symptoms, but they aren’t ideal, because tolerance is developed in less than a week and tolerance transfers between antihistamines. They also exacerbate some of my other health issues (POTS), so I forego them entirely these days.

If you do want to keep some around for the occasional intervention, it can be helpful to have Desloratidine or one of the other strong, fast acting ones on hand.

Try immunotherapy

I don’t know much about immunotherapy (it wasn’t a good fit for me when I tried it), but it’s been transformative for some friends. In the past few years, the option has been introduced to do immunotherapy by taking daily pills (instead of weekly shots), which makes it much more accessible.