Sheila Elcott asked:

I have an 11 year old red fox lab boy who keeps getting a build up of black coloured dandruff type patches under his chin & his manly areas. Up to date with spot on. Is it his age & lack of my grooming care? After bathing & removing said patches the skin clears. He has hip & elbow dysplacia to boot. Tnx

Answer:

Hi Sheila, thanks for your question. Skin problems in dogs can be really frustrating to deal with, so I’ll go through some of the possibilities, then talk about how they can be investigated and managed.

So, what can cause patches of black dandruff material to appear?

There are a number of possibilities that spring immediately to mind:

  • Flea dirt. Flea droppings are black flecks, sometimes comma-shaped.
    • I know you’re up to date with spot-on, but there are a wide range of different products out there, some of which are more effective and longer-lasting than others. In addition, most spot-ons are water soluble, so regular bathing or swimming will reduce their effectiveness.
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    • You’ll very rarely see a live flea unless there’s a really severe infestation. To check it out, try the wet paper test:
      • Scrape some of the black material onto a sheet of wet white paper.
      • If it goes red, it is probably a flea dropping – they’re basically just dried digested blood.
  • Scabs. As blood dries, it turns black and crumbly. It can be caused by:
    • Lice. Heavy louse infestation can cause scabbing where the parasites suck.
    • Skin infections. In these areas, this would typically be a skin fold infection, where saliva or moisture is trapped against the skin, damaging it and allowing infection to become established.
    • Allergic reactions (e.g. contact dermatitis). Reactions to products such as surface cleaners, pesticides, some plants, etc etc; typically affect the high-contact surfaces – chin, elbows, hocks and belly.
  • Sebaceous matter. Sometimes, excessive secretion of sebum may give the symptoms you’re discuss. This may be due to sebaceous adenitis (an inflammatory disorder), or simply from aging changes.

Unfortunately, without seeing the dog, it’s difficult to know which of these is the most likely for your boy!

So where do we go from here?

Ideally, you want to rule out parasites – do a wet paper test; and ask your vet to do skin scrapes and tape strips to examine the black material and the skin underneath it. Also, try and see if there’s anything that seems to trigger an episode – for example, if it always flares up after using a particular floor cleaner, I’d be really suspicious it was an allergic reaction.

So what can be done?

If a specific cause can be identified, obviously it should be treated (for example, a louse infestation should be treated; and you should avoid using any products that your dog is allergic to).

Even if not, there are certain techniques that may be useful in controlling the symptoms. As the problem resolves with cleaning, I’m quite suspicious that it might be a skin-fold infection – these are often more common in older dogs. In general, these can be controlled with grooming, good hygiene, and the use of medicated antiseptic wipes (e.g. CLX wipes) to control the growth of bacteria in the area. Sometimes, bathing with an antiseptic shampoo can help as well – you should talk to your vet about the options.

I hope that helps and you can get him sorted out!

David Harris BVSc MRCVS

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