It’s upsetting to watch your pet scratch a lot. You feel bad for your pet, there is more fur in the house to clean up… the scratching may even prevent you from sleeping! To make your pet feel better, we have to figure out what is causing your pet to itch.
There are 3 main reasons to itch and we will discuss each in this handout. But how do we determine which of these reasons is causing your pet to scratch? First we’ll need some answers:
- How long has your pet been itching?
- What areas of his body does he scratch?
- Has your pet been itchy before and, if so, what time of year did he itch in the past?
- What, if any, flea/tick preventives are you using?
- Are there any other family members, human or animal, also itchy?
After gathering this information from you, we will examine your pet’s skin looking for fleas, areas of hair loss or redness, and crusts or pustules. We may perform diagnostic testing such as skin scrapes to look for mites and cytology and cultures to look for infection. With all this information gathered from you and your pet, we can determine the likely cause of your pet’s scratching.
#1 Skin Parasites
An easy answer to the source of itching is that your pet has a external parasite like a flea, but we rarely luck out with an easy answer. Still, fleas can cause significant itching if they are present . A pet who is allergic to flea bites (the saliva from the flea bite is the source of the allergic reaction) may be very itchy even if he or she only has a few bites. Since it may be difficult to find fleas when only a few are present, we may recommend using an effective flea product, even if we do not see any fleas or flea dirt.
Another skin parasite that causes itching is skin mites, a condition called mange. There are two commonly seen mites: Demodex and Sarcoptic mites, which are diagnosed only in dogs. Demodex mites are more commonly seen in puppies whose immune systems are still developing. Sarcoptic mites, also known as scabies, can cause intense itching and some dogs will be so uncomfortable that they may become very sick. Sarcoptic mites are spread by contact with fur from infected dogs, fox or coyote. People who have contact with an infected dog can have skin irritation from the mite exposure, but this irritation will resolve when the dog is treated. Mites are diagnosed with a skin scraping, however the sarcoptic mite is often difficult to find. The monthly flea & tick preventatives, Simparica and Revolution, prevent and treat both mange and fleas. When pets are on these products, we can rule out parasites as a cause of their scratching.
A second common cause of itching is infection. Infections are caused by fungus (ringworm), bacteria, or yeast (malassezia). Ringworm is spread to both animals and people through contact with infected fur and is diagnosed by performing a fungal culture. Bacteria and yeast are normally present on skin in very small numbers but, when the skin’s defenses are compromised, the bacteria or yeast can multiply. Infections occur when the skin’s immune system is compromised by factors such as trauma from scratching due to allergies, heat, humidity, friction in areas such as arm pits, between toes, etc., and hormonal conditions such as hypothyroidism. If your pet has pustules or crusts, he likely has a bacterial (staphylococcus) infection. Yeast infections often cause an odor and greasy feel to the skin. By looking at a skin sample under the microscope, we can confirm if infection is present. Both yeast and bacterial infections are often treated with systemic antifungals or antibiotics. Topical medications, in the form of shampoos, mousses, or wipes can also help, especially to prevent recurrence of the infection.
We diagnose allergies, the third reason for itching, only when both parasites and infection have been ruled out. Therefore, it is very important that we evaluate your pet carefully to be sure neither is present prior to diagnosing an allergy. There are 2 types of allergies, food and environmental (atopy). See our separate handout on each allergy type. If this is the first time your pet is itching, or your pet itches throughout the year, then he could have either type of allergy. In these cases, a food trial can be done to see if the itching improves. If your pet itches around the same time each year, or if your pet does not improve with an appropriate food trial, then he likely has an environmental allergy.
Regardless of the cause of itching, we can prescribe medication to provide your pet some relief. Once we’ve determined the specific cause of itching, additional therapies can be prescribed to address the actual cause.