By Dial A Vet Veterinary Team
If your dog's itch is concentrated on the belly, the inside of the legs, the paws or the chin, and seems worse after time in a particular part of the garden, contact dermatitis is worth considering. It is less common than flea allergy or environmental allergies, but when it is the cause, finding and removing the trigger can make a dramatic difference. In Australia, one creeping garden weed is behind a surprising number of cases.
Key takeaways
- Contact dermatitis is skin inflammation caused by something touching the skin.
- It affects sparsely haired areas: belly, groin, armpits, chin, feet, and the scrotum in male dogs.
- Irritant contact dermatitis (direct chemical damage) is more common than true allergic contact dermatitis.
- Wandering trad (Tradescantia fluminensis), often called wandering jew, is a well-known Australian trigger.
- Diagnosis usually involves avoiding the suspected trigger and watching for improvement.
Irritant versus allergic contact dermatitis
- Irritant contact dermatitis happens when a substance damages the skin directly. Any dog exposed to enough of it will react, often after a single contact. Examples include strong cleaning products, fertilisers, chemicals spilt on the floor, or soap left on the skin after a bath.
- Allergic contact dermatitis is an immune reaction that develops after repeated exposure. Only some dogs become sensitised, and the reaction may take a day or two to appear after contact.
The signs look similar, but the distinction helps your vet work out what to remove.
Signs to look for
- Red skin, small bumps or a rash on the belly, groin, armpits, chin, paws or between the toes
- Itching, licking and chewing in these areas
- Hair loss and darkened, thickened skin in long-standing cases
- A sharp line where the rash stops at the edge of the fur
- Scrotal redness in males
The hair coat acts as a barrier, which is why contact reactions usually spare heavily furred areas such as the back.
Common triggers in Australian homes and gardens
- Wandering trad (wandering jew). A shade-loving ground cover common in damp gardens, particularly along the east coast. Many itchy dogs improve markedly once it is removed.
- Other plants such as some grasses, Moses-in-the-cradle and other Tradescantia species, and some bark and mulch products.
- Carpet cleaners, floor cleaners and disinfectants, especially if not rinsed well.
- Fertilisers, herbicides and garden chemicals.
- Plastic or rubber food bowls and toys, causing redness on the chin and lips.
- Shampoos, flea products or topical medications.
- Fabric dyes or detergents on dog beds.
- Concrete, wool rugs or new carpet, less commonly.
How it differs from other allergies
- Flea allergy mostly affects the lower back, tail base and back legs.
- Environmental allergies (atopic dermatitis) usually involve the face, ears, paws, armpits and belly, and are often seasonal.
- Food allergies can affect the same areas, often year round, sometimes with gut signs.
Because the areas overlap, your vet will usually work through other causes too. Our articles on allergy testing and belly rashes in dogs explain these.
When to see a vet
Book an appointment if your dog's skin is red, itchy or broken, or if the itch is persistent. Seek prompt care if:
- The skin is raw, oozing, crusted or smelly
- Your dog has facial swelling, hives or breathing difficulty (possible acute allergic reaction, an emergency)
- Your dog may have been exposed to a garden chemical or swallowed a toxic plant
How vets diagnose it
- History and examination, including where the rash is and what your dog contacts at home and on walks
- Ruling out other causes such as fleas, mites, infection and other allergies
- Avoidance trial: removing the suspected trigger, or limiting your dog to certain areas, for several weeks to see if the skin improves
- Provocative exposure: reintroducing the suspected trigger to see if signs return
- Patch testing, occasionally, by a veterinary dermatologist, where possible allergens are applied to the skin under a dressing
How it is treated
The most effective treatment is avoiding the trigger. While the skin settles, your vet may recommend:
- Gentle bathing to remove irritants from the skin
- Prescription medication to reduce itch and inflammation
- Treatment for any secondary bacterial or yeast infection
- Barrier strategies, such as a light shirt or booties, in some cases
Avoid tea tree oil, essential oils and human creams, which can irritate the skin further or be toxic if licked.
Reducing exposure at home
- Remove wandering trad and other suspect plants from areas your dog uses. Wear gloves, because the plant can irritate human skin too.
- Rinse floors with plain water after cleaning, and let them dry before your dog walks on them.
- Use stainless steel or ceramic bowls.
- Wash bedding in a fragrance-free, gentle detergent and rinse well.
- Wipe your dog's belly and paws with a damp cloth after walks in grassy or garden areas.
FAQ
Can contact dermatitis develop suddenly?
Irritant reactions can appear within hours. Allergic contact dermatitis develops after repeated exposure, sometimes over months or years.
Is contact allergy contagious?
No.
Will my dog grow out of it?
Allergic contact dermatitis tends to persist, but avoiding the trigger usually keeps it under control.
How long until I see improvement after removing a plant?
Often within a few weeks, though it can take longer for thickened skin to recover.
Talk with a vet
If you suspect something in your home or garden is irritating your dog's skin, a Dial A Vet veterinarian can look at photos, talk through possible triggers and help you plan a sensible avoidance trial. Talk to a Dial A Vet vet.
References
- Merck Veterinary Manual: Contact dermatitis in animals
- Hensel P, Santoro D, Favrot C, Hill P, Griffin C. Canine atopic dermatitis: detailed guidelines for diagnosis and allergen identification. BMC Veterinary Research. 2015;11:196.
- Weeds Australia: Wandering trad (Tradescantia fluminensis)
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If you are worried about your pet right now, contact your local vet or nearest emergency animal hospital.