[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Ectoparasites](https://durgical.com/en/microbiology/groups/ectoparasites/) › Dermatophagoides and Blomia tropicalis

# Dermatophagoides and Blomia tropicalis

- Parasite
- Exam priority: medium

Microscopic mites in mattresses, pillows and carpets that eat skin flakes. Their droppings are a leading cause of allergic asthma and rhinitis.

Updated Nov 13, 2026

Also called: house-dust mites, ácaros del polvo

## Quick facts

**Type**
Parasite · [Ectoparasites](https://durgical.com/en/microbiology/groups/ectoparasites/)

**Gram / shape**
Oval

**Spread**
Not an infection · Shaking bedding · Humid

**Causes**
Allergic asthma · Allergic rhinitis and conjunctivitis

**Treatment**
Reducing allergen exposure

On this page

- The basics Key points
- At a glance
- Morphology
- Transmission
- Life cycle
- In Colombia
- Memory aid
- What the colours mean

- Clinical Virulence factors
- Diseases it causes
- Clinical picture
- Diagnosis

- Treatment Treatment
- Prevention

- Study Test yourself

- Connections Connections

## Key points

- Leading indoor allergen in asthma and perennial rhinitis.
- Dermatophagoides pteronyssinus and D. farinae worldwide; Blomia tropicalis in the tropics.
- Allergens are in faecal pellets; exposure is mostly in bed.
- Humidity under 50%, covers and hot washing reduce allergen.
- Mite tropomyosin cross-reacts with shrimp and Ascaris.

## At a glance

**Shape**
Oval, creamy white body with 8 legs, invisible to the naked eye

**Family**
Pyroglyphidae (Dermatophagoides pteronyssinus, D. farinae); Echimyopodidae (Blomia tropicalis)

**Type**
Free-living mites (arachnids); not parasites, but a major source of indoor allergens

**Size**
About 0.2–0.4 mm

## Morphology

- No eyes; they absorb water from humid air through the body surface.
- They feed on human and pet skin flakes softened by moulds.
- The allergens are in faecal pellets and body fragments, which settle in dust rather than staying in the air.

## Transmission

- Not an infection: people are exposed by breathing allergens in dust, mostly in bed while sleeping.
- Shaking bedding, sweeping or dusting lifts the particles briefly into the air.
- Humid, warm climates such as Colombian lowlands and the Caribbean coast favour large mite populations all year.

**Reservoir:** Mattresses, pillows, upholstered furniture, carpets, curtains and stuffed toys; Stored grain and food (some related storage mites)

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- The female lays eggs in dust where skin flakes collect, such as mattresses.
- A six-legged larva hatches and feeds on skin scales.
- It goes through two nymph stages with eight legs before becoming an adult.
- Egg to adult takes about one month in warm, humid conditions; adults live a few months.
- Below about 50% relative humidity mites dry out and populations fall.

## Virulence factors

- Mite allergens include enzymes that damage the airway lining and promote allergic (type 2) inflammation.
- Tropomyosin from mites cross-reacts with that of shrimp and Ascaris, which can link food allergy, helminths and asthma.
- Sensitisation in early life is a strong risk factor for asthma in children.

## Diseases it causes

- Allergic asthma [Asthma →](https://durgical.com/en/conditions/asthma/)
- Allergic rhinitis and conjunctivitis [Allergic rhinitis →](https://durgical.com/en/conditions/allergic-rhinitis/)
- Flares of atopic dermatitis [Atopic dermatitis →](https://durgical.com/en/conditions/atopic-dermatitis/)

## Clinical picture

- Perennial sneezing, nasal blockage and itchy eyes, worse at night and on waking.
- Asthma with cough and wheeze in sensitised children and adults.
- Symptoms often worsen when making beds, cleaning or in old, closed rooms.

## Diagnosis

- Skin prick tests with D. pteronyssinus, D. farinae and, in the tropics, B. tropicalis extracts.
- Specific IgE in serum; molecular tests for single allergens help choose immunotherapy.
- A positive test means sensitisation; it matters only if it matches the symptoms.

## Treatment

Reducing allergen exposure, plus standard treatment of rhinitis and asthma: intranasal corticosteroids, antihistamines, inhaled corticosteroids and leukotriene antagonists. Allergen immunotherapy with mite extracts can change the course of the allergy in selected patients.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

- [Fluticasone](https://durgical.com/en/pharmacology/fluticasone/)
- [Budesonide](https://durgical.com/en/pharmacology/budesonide/)
- [Cetirizine](https://durgical.com/en/pharmacology/cetirizine/)
- [Loratadine](https://durgical.com/en/pharmacology/loratadine/)
- [Montelukast](https://durgical.com/en/pharmacology/montelukast/)

## Prevention

- Allergen-proof covers for mattresses and pillows.
- Wash bedding every week in hot water.
- Keep indoor humidity below about 50% and ventilate rooms.
- Fewer carpets, curtains and stuffed toys in the bedroom; damp dusting and vacuums with high-efficiency filters.

## In Colombia

In Colombian studies, sensitisation to Dermatophagoides is the most common in asthma, and Blomia tropicalis is also an important tropical mite; in Cartagena, sensitisation to mites and Ascaris, partly through cross-reacting tropomyosins, was associated with asthma.

## Memory aid

Your bed is their buffet: they eat your skin at night and leave droppings that tighten your chest in the morning.

## Test yourself

Think of the answer, then tap the question to see it.

## Which part of the house-dust mite carries most of the allergen?

Its faecal pellets and body fragments, which settle in bedding, carpets and furniture.

## Which environmental factor most controls mite populations?

Humidity: mites dry out and decline when indoor relative humidity stays below about 50%.

## Which tropical mite should be included in skin tests in Colombia?

Blomia tropicalis, together with Dermatophagoides pteronyssinus and D. farinae.

## Why can mite allergy relate to Ascaris and shrimp?

Because their tropomyosins are similar and IgE against one can cross-react with the others.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/dermatophagoides-and-blomia-tropicalis/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

## Connections

## Related 4

- [House flies and cockroaches](https://durgical.com/en/microbiology/house-flies-and-cockroaches/)
- [Ascaris lumbricoides](https://durgical.com/en/microbiology/ascaris-lumbricoides/)
- [Demodex folliculorum and Demodex brevis](https://durgical.com/en/microbiology/demodex-folliculorum-and-demodex-brevis/)
- [Sarcoptes scabiei](https://durgical.com/en/microbiology/sarcoptes-scabiei/)

## Related conditions 3

- [Asthma](https://durgical.com/en/conditions/asthma/)
- [Allergic rhinitis](https://durgical.com/en/conditions/allergic-rhinitis/)
- [Atopic dermatitis](https://durgical.com/en/conditions/atopic-dermatitis/)

[← Back to the group: Ectoparasites](https://durgical.com/en/microbiology/groups/ectoparasites/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Dust Mites | American Lung Association](https://www.lung.org/clean-air/indoor-air/indoor-air-pollutants/dust-mites) (American Lung Association, 2024); [Dust Mites and Cockroaches | National Institute of Environmental Health Sciences](https://www.niehs.nih.gov/health/topics/agents/allergens/dustmites) (NIEHS (NIH), 2025); [IgE responses to Ascaris and mite tropomyosins are risk factors for asthma](https://perfilesycapacidades.javeriana.edu.co/es/publications/ige-responses-to-ascaris-and-mite-tropomyosins-are-risk-factors-f/) (Clinical and Experimental Allergy (record at Pontificia Universidad Javeriana), 2015); [Allergic rhinitis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000813.htm) (MedlinePlus (NLM), 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/dermatophagoides-and-blomia-tropicalis/