Wednesday 21 March 2018

Hot spots cause serious discomfort for dogs

Golden Retrievers are especially prone to developing hot spots
Golden Retrievers are especially prone to developing hot spots

Pete Wedderburn - Animal Doctor

Sam the Golden Retriever had been normal when his owner went to work that morning. At lunchtime, she noticed that he had a damp patch on his fur over his tail, and she made a mental note to keep an eye on it.

By the time she came home at 5pm, the damp patch had turned into a balding, red, painful area as big as her hand. Sam had started to lick at it furiously, and it was clearly bothering him immensely. She brought him down to see me that evening: what was going on ?

Sam was suffering from a classic summertime dog problem. It's known colloquially as a "hot spot", while the veterinary technical title is a "surface pyoderma". Both expressions describe the problem clearly.

A "hot spot" is exactly what this looks like: a patch of skin that is bright red and overheated. If you put your hand near it, you can feel the heat coming off it. If you used an infrared camera, you'd see the affected patch of skin standing out like an overheated sore thumb.

Meanwhile, the term "surface pyoderma" describes what's happening at a pathological level. "Surface" because the problem is on top of the skin, outside the main substance of the skin layer. And "pyoderma" means "pus on the skin", because the reason for the heat, redness and itchiness is a bacterial infection on the skin surface.

But why does this happen? What goes so suddenly and dramatically wrong? Why should a dog be normal in the morning only to be battling a serious skin infection in the afternoon?

Every case can have a different, unique underlying cause, but the main sequence of events is as follows.

First, something sets up an initial irritation. This can be a physical cause, such as a flea bite, or an allergic reaction (e.g. pollens), but the bottom line is that the skin becomes temporarily damaged. The skin becomes red and sore - like a nettle sting. This type of minor irritation is common in dogs, and most often, the temporary irritation settles down within a few minutes. Again, the analogy of a nettle sting is useful: it hurts for a few minutes, then fades and vanishes.

The problem with "hot spots" is that they don't fade and vanish like nettle stings. Instead, the normal bacteria that live on the surface of the skin move in to the reddened area. Somehow they are able to break through the skin's normal defences, starting to multiply rapidly on top of the skin. The bacteria produce acids and other toxins that cause further irritation to the skin, causing even more redness and soreness.

Dogs like Golden Retrievers are particularly prone to this problem: they have a dense, insulating layer of fur, causing the skin level to heat up especially quickly, making the bacteria multiply more rapidly than ever.

At this stage, affected dogs start to aggravate the problem themselves. They can't help it: the patch of affected skin is very itchy and painful. The natural reaction is to lick, bite and scratch the hot spot, but unfortunately, this just makes it worse. The self-trauma causes further damage, and lets even more bacterial infection proliferate. A vicious circle kicks in: more damage, more infection, more redness and soreness.

The good news is that once this cycle of events is identified, it can be easily sorted.

When I saw Sam, I followed the standard series of five steps.

First, I cooled the area down instantly, by clipping off the fur over the red area, and for a one inch halo all around.

Second, I did my best to eradicate the bacteria that were perpetuating the problem, using an antibacterial scrub to clean the surface of the affected area, as well as a course of oral antibiotics to kill the bacteria from the inside out.

Third, I removed the redness and soreness from the hot spot, by applying a cortisone-based anti-inflammatory cream.

Fourth, I physically stopped Sam from damaging himself any further, by applying one of those dreaded "Elizabethan collars": the cone-like plastic device that stops a dog from licking sore areas.

The fifth and final step is an important one: to find out why Sam's skin had become red and sore in the first place.

Sometimes it's difficult to find the initial cause of a hot spot: an unknown allergy is suspected, and because it remains unknown, it can be difficult to stop it from happening again.

In Sam's case, the answer was simple: as I looked through his fur, I saw two clues.

First, there were some dark black specks no bigger than pinheads, like tiny pieces of soil. I picked them out, and placed them on some moist cotton wool. The black colour faded, and a reddish halo appeared around each speck. This confirmed that the specks were, in fact, "flea dirt", which is the digested blood that fleas leave behind them.

Second, to remove all doubt completely, I saw a flea scurrying through his coat.

So the sequence of events was clear: fleas had caused the initial irritation, bacteria then moved in to set up the skin infection, and Sam had made it worse by licking and chewing the sore areas of skin.

The answer was now simple: I just added flea control in to his treatment programme, giving him a long lasting tablet that would kill all fleas and protect him for three months. No more hot spots for Sam!

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