I'm sorry to hear that your dog is experiencing hair loss. There's a few possible causes here, and at the top of the list of suspects is a parasite infestation or a fungal infection. A bacterial infection an also cause hair loss, but this isn't too likely since you didn't mention any redness and swelling, as is characterisitic with a bacterial infection. Changes in skin pigment often occur when infection or irritation is present - it's a form of scarring in some pets, so this would support parasites or an infection. I'd be happy to go over some of the in's and out's of these conditions, but I would strongly suggest a vet visit as these conditions can worsen rapidly and you can't effectively treat them at home since we don't know exactly what is causing this.
There's a broad array of fungal infections that can affect our pets. Yeast infections result in a scaly, dry appearance, sometimes they ooze, and they're often very itchy. To diagnose this or a parasite infestation, your vet will scrape the very outer layer of skin away, and it will then be examined under the microscope for signs of fungi or parasites.
It's also possible that the skin was broken, even just slightly, which can occur when parasites are present, and this could have allowed for a bacterial infection to take hold. That too is a possibility that I would explore a bit further. As I mentioned, usually redness and inflammation is present, but there's always exceptions to the rule. Your vet would have to examine the area and take a culture to determine exactly what's going on.
Parasites are also a really good possibility. Your vet would have to diagnose these with a skin scraping or a fecal floatation test, but fortunately, treatment is inexpensive and usually pretty simple.
I also wonder if an allergy could be to blame, particularly a food allergy. Symptoms of a food allergy include itching, dry, flaky skin, rashes, and hair loss. This is something that will likely be investigated if all of the things I've mentioned above turn out to not be the case.
If she's not experiencing an infection or parasite infestation, it may be worth trying your girl on an exclusion diet for a week or so. You can try her on a bland "people food" diet - it will be easy on her stomach. I would recommend boiled hamburger or plain chicken with plain white rice or cottage cheese. This way, you'll only be feeding her two ingredients, and if she's reacting to one of the dozens of ingredients in her food, you should see an improvement when the allergen food item is removed from the equation.
In the meantime, I would be sure you're cleaning the area twice daily with an antibacterial soap. If it's itching, you can then apply some hydrocortisone cream. Then, I would apply a thin layer of antibiotic ointment, just in case you have an infection brewing.
Here's a couple of good websites that describe the different fungal infections and other similar conditions: http://www.marvistavet.com/html/body_yeast_infection_of_the_skin.html http://www.sniksnak.com/doghealth/ringworm.html http://www.thepetcenter.com/gen/itch.html http://www.pet-supplies-review.com/dog-yeast-infection.html http://www.canismajor.com/dog/mange1.html http://www.thepetcenter.com/exa/mites.html http://www.doggiesparadise.com/dog-skin-disorders.shtml
I hope this gives you a few new directions to explore with your dog! Don't hesitate to let me know if you have any additional questions!
I hope your dog is feeling better soon!
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