Kirby, Are You OK?

There's a strange thing happening with Kirby that has me a bit worried.  When he was a puppy he had a lot of dark hair in his coat but he had what I would call a light skin color.

His chest hair is dark but the skin beneath is a light color.

His chest hair is dark but the skin beneath is a light color.

Here you can see where he is starting to lose the black on his face

Here you can see where he is starting to lose the black on his face

As he got older his coat began turning a reddish blonde losing the black on his face and body.  The black on his back was barely noticeable unless his coat was wet. Over the last few months I've noticed his skin getting darker and his coat is regaining the black throughout his back, sides, and even the top of his head. The dog has a lot of black roots!

Of course I started googling for answers. The closest I got about the skin darkening was the following:

Cushings Disease can cause hair loss, thinning of skin, hyperpigmentation, easy bruising, seborrhea, comedones (black heads), may see calcinosis cutis; lethargy, increased thirst and urination, and a pot-bellied appearance.

Next was a food intolerance or allergy with the following symptoms: Non-seasonal itchiness of any body location, Poor response to anti-inflammatory doses of glucocorticoids generally suggests food hypersensitivity, VomitingDiarrhea, Excessive gut sounds, passing of gas, and frequent bowel movements, Malassezia dermatitis (fungal skin infections), pyoderma (bacterial skin infections), and otitis externa (inflammation of the outer ear), Skin plaques – broad, raised flat areas on the skin, Pustules – pus-containing raised skin inflammations, Erythema – redness of the skin, Crusts – dried serum or pus on the surface of a ruptured blister or pustule, Scale – flakes or plates of dead skin on the skin's surface, Self-induced baldness due to scratching, Abrasions/sores on the skin due to scratching, Leathery, thick, bark-like skin, Hyperpigmentation – darkening of the skin, Hives – swollen or inflamed bumps on the skin, Giant wheals (elongated marks) on the skin, and Pyotraumatic dermatitis – infection of the skin wounds due to scratching excessively, and bacteria entering the wounds.

I also discovered that Dachshunds may have this tendency. (Kirby is part Dachshund) Some of it may be the skin maturing to its natural color and this may be part of the natural aging process as well. However, there is a VERY COMMON condition in dachshunds knows as acanthosis nigricans which can occur in a benign form or in a "malignant" form. Only the malignant form requires concern. The most frequent version appears as dark skin in the armpits. ACANTHOSIS NIGRICANS: (dachshunds): a skin disease where the skin becomes thickened and dark, primarily affecting the axillae (armpits). ACANTHOSIS NIGRICANS: Overview (canine): Acanthosis nigricans is a poorly-understood condition in dogs in which the skin becomes blackened. The process typically starts in the armpits and groin and the skin becomes thick, greasy and heavily pigmented. Inflammatory pigmentation is common in dogs, but this condition is distinct. The diagnosis is verified by biopsies for histopathologic assessment. Treatment is sometimes successfiil with topical therapies, oral vitamin E, topical corticosteroids and injectable melatonin. Mode of Inheritance: Not known but presumed to be autosomal recessive or polygenic.

Being a responsible pet pawrent, plus the fact I love this dog beyond reason, I promptly made an appointment with his veterinarian. A full assessment revealed Kirby weighed 14.6 lbs (good), and overall appeared to be in good health.  He's still very active with a healthy appetite, his skin is soft and his coat is soft and shiny. In fact his coat is getting longer and plusher on his chest where it used to be sparse.

Where his skin is darker is where his coat used to be darker

Where his skin is darker is where his coat used to be darker

Dr. Rita said we could do more formal tests such as blood work but she didn't see the need at this point since he showed no other symptoms to warrant the expense.  She even commented that maybe he was super healthy. Then we talked about any changes in his diet. There haven't been any. He still eats a rotational diet of homemade foods and his morning commercial kibble is the same he's been eating for the past three or four months.

The one change was his monthly flea and heartworm meds.  Last summer I gave up on home flea remedies and started him on Comfortis. Roughly two months ago I ran out of his Iverhart heartworm med so I switched him to Trifexis (spinosad + milbemycin oxime) which contains the same ingredients as the Comfortis (spinosad) and Iverhart (ivermectin/pyrantel pamoate/praziquantel) but also protects against roundworm, hookworm and whipworm. All this medical terminology is just too confusing for me! It was time for his monthly meds so I went back to the Comfortis and Iverhart.  

I honestly don't know if the Trifexis is causing anything harmful so please don't go "warning" others just yet. For now I'll keep a close eye on Kirby for any alarming symptoms or any improvements or changes. The main reason I'm sharing is not to alarm but to see if any other dogs have/are experiencing this strange phenomenom?

Worried pawrent seeking advice