What are mites?
Mites are tiny insects that are found in a variety of habitats, such as water, soil, woods, fields, and houses. Many mites are microscopic in size, and are very difficult to see with the naked eye. Like spiders, mites belong to the class Arachnida. Along with ticks, mites constitute the subclass Acarina. The discipline that involves the study of mites and ticks is known acarology.
Mites can attack a variety of organisms, such as plants, animals, and humans. However, not all mites attack the same host species. Examples of mites that attack and bite humans include scabies mites, house dust mites, itch mites, chiggers, and Demodex mites. Even without biting, some mites are capable of triggering an allergic skin reaction in humans. A common sign of such an allergic reaction is development of an itchy skin rash. It is important to note that not all mites cause harm to humans. Many are harmless to our species.
House Dust Mites
House dust mites (HDM) get their name from their preferred habitats – dusty places. These microscopic creatures (mostly belonging to Dermatophagoides spp.) are found all over the world. They can be seen all year round, and prefer dusty, moist, and poorly ventilated places. House dust mites are commonly found on mattresses, carpets, pillows, beddings, furniture, and curtains. It is important to note that house dust mites are not exclusive to “dirty homes”. They can also be found in houses that are relatively well-maintained.
Dust mites thrive on dust. They do not bite or feed on human skin. Instead, they derive nutrition from pollen, fungi, and bits of dead skin that fall off animals (including humans). However, house dust mites may be problematic for individuals who are allergic. House dust mites may cause aggravation of wheezing, sneezing, asthma, runny nose, and atopic dermatitis in people who have allergies. An allergologist can diagnose allergies to dust mites.
Preventing House Dust Mite Exposure
The following are some of the measures one can take to prevent exposure to dust mites in the house:
- Keep your home dry. Dust mites die when the humidity levels in the air fall below 60%. It is important to note that dust mites cannot be killed with commonly used household cleaners.
- Keep the rooms where you spend a lot of time (such as the bedroom) free of heavy curtains, carpets, pets, and soft toys.
- Use a vacuum cleaner to clear dust from all surfaces which tend to get dusty.
- Wash beddings every week using hot water. Change bedding every week.
- Steam wash or shampoo wash carpets at least once a year, especially during the spring season.
- Use HEPA air filters to prevent pollen and dust from accumulating in your home.
- Do not sleep on the floor.
Scabies mites are transmitted via long time personal contact with people who already have the mites on them. It is rare to contract scabies mites from bed linens. Also, scabies does not spread through animals. Almost anyone can get scabies mites. The possibility of getting attacked by scabies mites does not depend on the hygiene levels.
Scabies mites are found all around the world. These mites spread easily in human communities where individuals stay in close proximity to each other (such as student hostels and prisons). Scabies mites burrow into the human skin. However, their burrows are usually limited to the superficial layers of the skin.
Read more about scabies.
A red, bumpy rash or S-shaped, tiny canals may appear in the skin areas where the scabies mites have burrowed into the skin. Scabies mites often burrow into the skin of the elbow, wrist, fingers, toes, armpits, waist, shoulder blades, penis, around nails, under rings, around nipples, and under watch straps. In children or individuals with low immunity, the scabies mites may also affect the face, neck, head, soles, and palms.
Scabies mites may also elicit an allergic reaction that is characterized by intense itching. The itch is especially intense at night, and may occur all over the body. Upon first infection, the itching usually occurs 2-8 weeks after the infection. However, itching may begin earlier (within 1-4 days) with subsequent infections. Scratching the skin in an attempt to get relief from the itching sensation could damage the skin. The damaged skin areas are prone to getting Staphylococcus infections.
In elderly individuals or people with low immunity, scabies can be very intense. This severe form of scabies (known as Norwegian or crusted scabies) is characterized by the appearance of skin crusts. Crusted scabies is a highly contagious form of scabies due to the presence of a large number of scabies mites inside and on the skin.
Diagnosis of scabies mite infection is done via microscopic analysis of skin scrapings.
Scabies can be treated by body-wide application of Crotamiton or Permethrin cream or lotion. Ivermectin pills are prescribed for treatment of both Norwegian and common scabies. Nails should be cut short and kept clean to avoid spread of mites through scratching. It is important to note that the itching may continue for a few weeks even after successful treatment of scabies. This may be due to an allergic reaction. In such cases, antihistamines, elimite cream, or oral steroid medications may be given to provide relief from itching.
If the itching at the fingertips does not subside after treatment, one can soak the digits in warm water for some time. Once the skin gets a raisin-like appearance, the surface of the skin can be scraped to remove the dead mites.
Since scabies is a contagious condition, all individuals who are in close contact with an infected individual should also be treated for scabies.
Direct skin contact should be avoided to prevent the spread of scabies. Also, personal items of a scabies-infected individual should be washed thoroughly in warm water. If an item cannot be washed, it should be sealed for at least 72 hours to let the scabies mites and their eggs die. A thorough cleaning of an infected individual’s living quarters may be done in case of Norwegian scabies.
Chiggers are tiny, red-colored, hairy mites that are found in the woods or grasses. They belong to the Eutrombicula species. Chiggers can live off human and animal skin. When they bite, they leave their saliva on the skin. The saliva dissolves skin particles that the chiggers then consume. A characteristic feature of chigger bites is the appearance of red, itchy welts on the skin. These are mostly seen on the skin around the ankles, knees, waist, and elbows.
Chiggers can be easily rubbed off the skin. Washing also removes chiggers from the skin. Insect repellents are helpful in keeping chiggers away. Also, while walking in the woods or on grass, it is advisable to wear long pants, shoes, and long-sleeved shirts to prevent chiggers from gaining access to naked skin.
Read more about chiggers.
Human Demodex Mites
Demodex mites live in the hair follicles and sebaceous glands. Eyelashes and eyebrows are the most common dwelling places for Demodex mites. In many cases, these mites can live within the hair follicles without causing any uncomfortable symptoms.
Some of the common signs and symptoms caused by these mites include itching of the eyelids or eyes, dryness and redness in the eyes, loss of eyelashes, blurry vision, and redness or scaling of eyelids. Microscopic examination of pulled eyelashes confirms the presence of Demodex mites. However, diagnosis of this condition is relatively rare since the mites do not cause any symptoms in many cases.
Treatment and Prevention
Treatment for Demodex mites consists of scrubbing the eyelids with a 1:1 dilution of baby shampoo, overnight application of antibiotic ointment, and treatment of eyelid margins with 70% alcohol, ether, and proparacaine. Preventive measures include use of clean bed sheets, avoiding eye makeup, and checking pets and other family members for the presence of Demodex mites.