Ear Mites in Dogs & Cats: Diagnosis & Treatment Guide

By Sarah Bennett, Certified Animal Nutritionist

If your dog or cat has been shaking their head persistently, scratching at their ears, or you've noticed a dark, crumbly discharge in the ear canal, ear mites should be high on your list of suspects. Otodectes cynotis is the most common cause of otoacariasis (ear mite infestation) in companion animals and accounts for a significant proportion of all otitis externa (outer ear inflammation) cases in cats and a notable portion in dogs. The good news: ear mites are easy to diagnose and very straightforward to treat once identified.

What Are Ear Mites?

Otodectes cynotis are tiny eight-legged parasitic mites — just barely visible to the naked eye as tiny white moving dots. They live their entire life cycle on the host animal, spending most of their time in the ear canal feeding on skin debris, ear wax, and tissue fluids. Their complete life cycle — from egg to adult — takes approximately three weeks. Female mites produce eggs that are glued to the skin of the ear canal and hatch within four days. Without a host, adult mites can survive for only a few days in the environment; however, they spread extremely readily through direct contact between animals.

While the ear canal is their preferred habitat, ear mites can occasionally be found on the skin elsewhere on the body — particularly along the tail and rump when the animal curls up to sleep. This can cause skin irritation and papular dermatitis in areas beyond the ears.

Signs and Symptoms

The classic presentation is difficult to miss once you know what to look for. The most obvious sign is the dark brown to black discharge that accumulates in the ear canal. This discharge has a characteristic appearance often described as "coffee grounds" — it is a mixture of ear wax, dried blood, mite faeces, and debris. It is distinct from the yellow or brownish discharge associated with bacterial or yeast ear infections, though these can occur concurrently as secondary infections.

Intense scratching at the ears and around the head is almost universal. The irritation caused by mites — both from their physical presence and the body's immune response — causes relentless itching. Head shaking is another common sign, as the animal tries to dislodge the source of irritation. In severe or long-standing cases, the constant scratching can cause self-trauma: wounds, crusting, and even haematoma (blood blisters) of the ear flap, which sometimes require surgical drainage. In very young or severely affected animals, partial hearing loss from extensive canal debris is possible.

Diagnosis

Diagnosis is typically made by a veterinarian using an otoscope to visualise the ear canal. Under magnification, the mites themselves are visible as small white moving points in the dark debris. A swab of the discharge examined under a microscope confirms the diagnosis by revealing mites, eggs, or faecal pellets. In some cases, the mites may be less numerous and harder to spot — a thorough clinical examination combined with the history and symptom picture usually allows for a confident diagnosis.

It is worth noting that ear mites are not the only cause of dark ear discharge. Yeast infections (Malassezia) and bacterial otitis externa can look very similar. If treatment for ear mites does not resolve the problem, further investigation for other causes is warranted.

Treatment Options

Modern ear mite treatments are highly effective. The most widely used products contain either selamectin (Revolution/Stronghold), ivermectin, or milbemycin oxime, applied topically to the ear canal or as a spot-on to the skin. Spot-on treatments that cover ear mites — such as Revolution Plus for cats or Advocate for dogs — are convenient because they treat the whole body, not just the ears, ensuring any mites living outside the ear canal are also eliminated.

Older treatments include ear drops containing pyrethrins or monosulfiram, which require application every day for three weeks (to cover the full life cycle). These are less convenient but still effective. Before applying any treatment, the ear canal should be gently cleaned to remove the accumulated dark debris, which can impede the penetration of topical medications.

Treating All Pets in the Household

This cannot be emphasised enough. If your dog has ear mites and shares a home with a cat — or another dog — all animals must be treated at the same time, even if the others appear asymptomatic. Cats, in particular, can carry ear mites with minimal symptoms while spreading them readily to other animals. Treating only the symptomatic pet while leaving an asymptomatic carrier untreated is the most common reason ear mite infestations keep recurring.

Prevention

There is no dedicated ear mite vaccine, but regular use of broad-spectrum parasiticides that cover ear mites — such as Revolution (selamectin) or Advocate (imidacloprid + moxidectin) — provides ongoing protection. Regular ear cleaning with a veterinary-approved ear cleanser helps remove accumulated debris and allows early identification of any discharge changes. Avoiding contact with stray animals is also advisable, as they represent a significant reservoir for ear mites.

References

1. Saridomichelakis MN, Farmaki R, Leontides LS, Koutinas AF. "Aetiology of canine otitis externa: a retrospective study of 100 cases." Vet Dermatol. 2007;18(5):341-347. PMID: 17845734
2. Six RH, Becskei C, Mazaleski MM, et al. "Efficacy of sarolaner, a novel oral isoxazoline, against two common mite infestations in dogs: Demodex spp. and Otodectes cynotis." Vet Parasitol. 2016;222:62-66. PMID: 27161861

Written by Sarah Bennett, Certified Animal Nutritionist. This article is for informational purposes only and does not substitute professional veterinary advice.