Summer Skin Diseases

Not So Fun In The Sun

      Summer is my favorite time of year. I love wearing flip-flops, going to the beach and having folks over for a good BBQ. But there is one thing I hate about summer - all the gross, stinky, oozing, crawling, inflamed skin diseases we see on our cat and dog patients. Summer is prime skin disease time and it is no fun at all, not for our patients or our clients. Why do we see so much skin disease during the summer? There are many reasons. As you should know, summer is often hot and humid. This makes people want to take their dogs swimming, go on a hike or just play outside. Combine moisture (i.e. the local lake or the suffocating humidity) with some scratches or bug bites and you have the start to many a hot spot or pyoderma. Summer is also the time everything likes to bloom and pollinate, contributing to many allergic skin diseases and recurrent flare-ups. And fleas love the summer! All that heat and humidity is just prime flea-breeding weather. Even with all the excellent flea and tick preventatives on the market, we still see a lot of flea infestations and flea allergies. In this article, I want to focus on the four most common skin issues we see during the summer - pyoderma, hot spots, flea allergies and seasonal allergies.

            Pyoderma is a fancy name for a superficial bacterial folliculitis or skin infection. It is usually caused by a species of Staphlococcus, although not the same species that affects people. On normal healthy skin, bacteria do not typically cause a problem. Pyoderma usually develops because something has changed in the skin to make it susceptible to infection. Allergies, external parasites like fleas or other skin-related issues like seborrhea can all contribute to the development of pyoderma. It occurs most frequently in dogs and rarely in cats. And what does pyoderma look like? It typically appears as focal, multi-focal or generalized areas of red pustules, crusting papules, hair loss and very red/inflamed skin. It usually involves the ventral abdomen (belly), axillary region (armpits) and neck, and affected animals can be very puritic (or itchy).

            Treatment is two-fold. First, we must address the infection itself with antibiotics. A course of steroids is often prescribed to decrease the inflammation and help keep the animal comfortable. Depending on the extent of the pyoderma, some animals must be clipped to allow air to get to lesions or for the application of topical products or medicated shampoos. The second step is to treat the underlying cause, if one can be found. Fleas, obviously, must be killed. If swimming in lakes or running through long grass triggers allergies, this must be stopped or animals washed more frequently to decrease allergen contact on the skin. Allergies or endocrine disorders must be considered. Sometimes, no underlying cause can be found and treatment merely addresses the current infection and puritis. Most animals recover within two weeks, unless there is some other issue such as chronic allergies.

            A related and often more acute summertime problem are "hot spots". A "hot spot" is a layman's term for pyotraumatic dermatitis or acute moist dermatitis. It is an acute and rapidly developing surface bacterial skin infection that occurs secondarily to self-inflicted trauma. This is also more common in dogs than cats. These can occur anytime during the year, but we tend to see them more in the warmer months. Owners will often describe these lesions as "appearing overnight" because they develop so rapidly. Hot spots can be precipitated by many things - insect bites, scratches, external parasites, etc. Dogs will scratch or lick the sites excessively, leading to the rapid development of a hot spot. It appears as an area of inflamed, weepy, moist, almost ulcerated lesion on the body and it can be very uncomfortable.

Hot spots must be treated quickly and aggressively because they can spread so rapidly and are so uncomfortable for the animal. Any underlying cause must be addressed first. The site is clipped and cleaned, occasionally with the need for sedation in a particularly painful animal. Topical agents (drying and analgesic), oral antibiotics and steroids are all used, and further self-trauma must be stopped, usually by way of an e-collar. Lesions usually resolve within two weeks.

            This year has been a particularly bad year for flea infestations. As I mentioned before, fleas love hot, humid weather and we've had an overabundance of that this summer. So, we've been seeing a lot of flea allergic animals. These animals are ITCHY! Flea bites are itchy regardless, but these animals are hypersensitive to flea saliva. Both cats and dogs are affected. Animals will suffer a number of skin lesions including hair-loss (alopecia), inflammation, excoriations, crusts, seborrhea, and hyperpigmentation. They are often quite miserable. Cats will typically display a "miliary dermatitis" or moth-eaten appearance to their coat, especially along the trunk and hind end. Flea allergic dermatitis (FAD) often leads to secondary pyodermas or hot spots in dogs. Fleas or flea dirt are tell-tale signs, but fleas may not always be obvious. It may only take one or two fleas to precipitate a flare-up of FAD in sensitive animals.

Treatment is two-fold. First, the affected animal is treated, usually with steroids for the puritis (itchiness) and antibiotics for secondary infections. Second, the fleas MUST be treated. If your animal has fleas, your house has fleas!! All animals in the house must be treated with a reliable topical product such as Frontline or Advantage. The house must also be treated. It is a big, fat frustrating pain to get rid of fleas once they are in your house and treatment needs to continue for at least three consecutive months, if not for all warm months and into the winter. Flea allergies can be very frustrating to treat because fleas are difficult to kill once established in a house and these animals are itchy and miserable until all the fleas are gone.

Now, all of the above dermatological issues may be related or cause by underlying allergies - either food or environmental. Allergies are one of the most frustrating disorders to treat for multiple reasons. They can manifest in a number of ways and cause a variety of clinical signs from chronic otitis externa (ear infections) to gastrointestinal issues to dermatological conditions (pyoderma, puritis, etc). They may be seasonal or year-round. Summer is obviously a bad time for many allergic dogs because plants are spreading pollen like nobody's business. Some unlucky dogs are also allergic to indoor allergens such as dust mites or cat dander, or they have concurrent food allergies (which is another kettle of fish altogether). Seasonal allergies tend to be slightly easier to diagnose because they have a more obvious seasonality and rhythm. If your dog or cat has the same skin issue every June and only in June, it can often be assumed they are allergic to something blooming in June and therefore have a seasonal allergy.

There is no one simple way to treat or manage allergies. Every animal is a little different. Some can be maintained comfortably on just antihistamines and medicated baths. Others need long-term steroids and recurrent antibiotic therapy. More severely affected animals (or those that have year-round allergic issues) may need to pursue allergy testing, specialized diets or other chronic medication use. And since allergic disorders can present in many ways, a veterinarian cannot simply look at an animal and declare them as allergic. Other dermatological differentials must be ruled-out first (like ringworm, demodex mites, endocrine disorders, etc). Secondary infections like pyodermas or hot spots must be treated and controlled as well.

Treating allergies can be very frustrating for owners, animals and veterinarians. They often require significant dedication from owners to help manage, diagnose and treat these animals. In fact, all of the above dermatologic disorders can be equally frustrating and recurrent in some cases. Skin diseases are not always a simple "give him a shot and fix 'em, doc" cure. Yes, the treatment in some cases is easy enough. Uncomplicated hot spots and pyodermas respond very well to therapy, but others are not always so lucky. If you or your veterinarian suspects your pet has an underlying allergic condition, take the time to discuss it and decide on the best course of prevention and treatment. If you understand the underlying causes and predisposing factors, hopefully you can manage your animal's summer skin diseases better or even prevent them from occurring. Summertime should be about fun in the sun - not itchy, red, oozing, crusting, ulcerated skin!

Some information from this article was developed from Small Animal Dermatology: A Color Atlas and Therapeutic Guide by Linda Medleau and Keith A. Hnilica.