External parasites that can affect dogs

Jun 21, 2022

External parasites are small hosts that lodge in the different layers of the dog’s skin. In addition to being annoying for the animal, they can cause injuries of varying severity, both due to an allergic reaction on the part of the dog, and due to the transmission of diseases of which they are potential carriers, such as leishmaniasis or heartworm. Normally there is a greater presence of these organisms in spring and summer, since the ideal conditions for their proliferation are given. In early stages, they generally cause itching and discomfort, but if this worsens, they can lead to more serious problems that can compromise the animal’s health.

The main external parasites that affect dogs are mites, fleas, ticks, mosquitoes and sandflies.


They are very small insects with a flattened brown or black body, which move quickly through the animal’s body, so they are usually detected by the dirt left on the fur, the result of their droppings. However, when the dog is dark in color, its detection is more complicated. The warm and humid climate favors the development of fleas that can become a seasonal or permanent problem depending on the climate.

Fleas can cause irritation and a feeling of itching and discomfort, which means that the dog is constantly scratching, triggering skin infections. Younger or smaller animals that are infested with fleas may become anemic. An infestation can happen relatively quickly, as each flea can lay between 300 and 400 eggs.

They can transmit infectious and parasitic diseases to pets and rarely to people. The most common damages are itching and irritability in the animal, and if it is allergic they produce DAPP (Allergic Dermatitis due to Flea Bite), giving rise to skin inflammation, severe itching and hair loss.


Ticks, unlike fleas that move through the skin, embed themselves in it to feed on the animal’s blood. Their greatest seriousness is that they are carriers of many diseases, some of which can be very serious. The most common are Lyme disease or piroplaxmosis or babesia, a disease that if not treated in time can be fatal since the parasites attack the red blood cells, potentially affecting vital organs.

Normally they appear and proliferate with the arrival of heat and humidity, optimal conditions for their development. They like the dog’s ears and neck, although they can be found anywhere, and locating them is relatively easy by touch. When we locate the tick, they must be removed correctly, otherwise part of the insect may remain inside the animal’s skin, causing infections. To remove them there are special tweezers, or if you can’t go to the vet.


Mites are microscopic parasites that settle on the dog’s skin and can cause diseases such as mange. There are three types of mites that affect dogs, one of them present in the ears, and the other two in the skin, producing the two types of canine mange: sarcoptic and demodectic.

This parasite leads to skin irritation, hair loss and scabs. If the disease is not treated, it can cause more serious internal disorders.

The sarcoptic mange mite produces mange and consequently the dog scratches in a very exaggerated way. Demodectic mange mites are not as contagious as the former, but when the population of these organisms increases, it produces demodectic mange disease, which can be localized or generalized. When it is localized it can be relieved relatively easily, however, if it is generalized it is a major problem that can end with the death of the animal. The first symptoms are localized hair loss, and over time this can lead to collateral complications such as bacterial infection of the skin or pyoderma, leading to swollen glands, suppuration and a bad smell.

There are also ear mites, more similar to the sarcoptic mange mite, and as the name indicates, they are located in the animal’s ears. The presence of these organisms leads to intense itching, which the dog will try to alleviate with scratches that can end in injuries.

Sandflies and mosquitoes

Mosquitoes are another of the external parasites that can affect dogs. They pierce the animal’s skin in order to feed on its blood, and can transmit diseases to dogs, some of them as serious as heartworms. Sandflies are much smaller than mosquitoes, but they feed in the same way, and they are transmitters of leishmaniasis.

How to avoid them?

Treatment of external parasites

Like any treatment, it should always be under veterinary supervision. There are many products on the market both to prevent the presence and colonization of external parasites, as well as many treatments of different formats and duration.

Proper hygiene of the animal, as well as its environment, will also be a determining factor in preventing the appearance and proliferation of these insects. This includes his toys, his bed, and the places where he usually lies down. In general, a thorough cleaning of the entire house is recommended to ensure that we eliminate both parasites and their larval forms, which can be in the most unexpected corners.

To avoid external parasites, there are different preventive methods, which under veterinary recommendation can be decisive in avoiding pests in animals. They come in different formats and durations, and some are more effective than others.

Repellent sprays for dogs

Antiparasitic sprays are applied to the dog’s body, camouflaging its smell and acting as a repellent against external parasites and reducing the probability of being bitten. Antiparasitic sprays should be used as a complement to other more effective methods.

Antiparasitic collars for dogs

Antiparasitic collars for dogs are placed on the animal’s neck, and release antiparasitic substances that act as a repellent against mites and insects that feed on blood. They have an effect of several months and their effectiveness depends on the brand, so it is always recommended to consult the veterinarian and seek advice to know which is the most suitable for each animal.

Antiparasitic pills for dogs

Antiparasitic pills are a fairly invasive method since they contain substances that, after being ingested, are distributed throughout the animal’s body until they reach the skin. These substances are toxic to the parasites that feed on the animal’s blood, so once they bite the animal, they soon die. The problem with the pills is that they do not prevent the bite, and only reduce the possibility of disease transmission, so it is recommended to always combine them with other methods such as the collar and pipettes.

Antiparasitic pipettes for dogs

Antiparasitic pipettes are capsules with liquid that repels external parasites that are applied directly to the dog’s back, since it is the only place that cannot be accessed with the tongue. The liquid is absorbed and acts as a repellent for a certain period of time, which is usually a minimum of one month.