Is atopic dermatitis in dogs contagious to humans? A Complete Guide

Clinical Signs of Canine AD

Canine AD is characterized by erythema and pruritus that preferentially affects some body areas [35]. Those areas include the muzzle, neck, chest, periocular areas, the pinnae, the antebrachial area, and the axillary and inguinal areas ( and ). Interestingly, these areas have been found to have increased permeability compared to other body areas [12] so it could be speculated that this may be a reason for why they tend to be preferentially affected. Pruritus is a consistent characteristic of this condition and it tends to worsen once secondary infections develop. Canine AD is aggravated by other allergies, such as flea allergy, and many patients may have overlapping signs of AD and flea allergy. The presence of multiple triggers plays a very important role in the management of pruritus as all triggers are additive.

AD develops in young individuals and it is initially, in most cases, seasonal. As time progresses, AD has the propensity to become year-round and to progressively increase in severity. Thus, the course is chronically progressive in the majority of patients. Secondary infections, both bacterial and yeast, frequently develop as self-trauma and inflammation makes the skin more vulnerable.

Despite many efforts to identify a “diagnostic test” for canine AD, the diagnosis remains clinical. A variety of clinical criteria [36,37] have been considered over the years with variable sensitivity and specificity. Regardless of the criteria, the diagnosis is based on history, clinical signs, and exclusion of other pruritic diseases. Detection of allergen-specific IgE is considered a minor criterion. Thus, allergy testing to detect allergen-specific IgE, both serology and intradermal skin tests, cannot be used for diagnostic purposes as they do not have a great ability to discriminate between normal and atopic patients [38]. Allergy testing is best used to identify allergens to include in allergen-specific immunotherapy once a clinical diagnosis of AD has been made.

Canine AD and Skin Barrier Abnormalities

The topic of the role of skin barrier abnormalities in canine AD is relatively new compared to what has been known in human medicine for decades. Yet, there is increasing evidence that some skin barrier dysfunction exists, although it is still unknown whether a primary skin barrier defect exists [7]. All of the studies so far have focused on comparing atopic dogs with healthy controls and have not compared the changes observed in atopic skin to what may be present in dogs with other skin diseases. This is of great importance before any definitive statement can be made about the specificity of the changes as it pertains to AD. It is indeed known that inflammation can worsen the skin barrier, thus, it is important to remember that some of the changes observed in inflamed atopic skin may be, at least in part, due to the presence of inflammation, whether that is clinically evident or only histologically present.

Currently, several studies have reported decreases in ceramides [8], alterations in filaggrin expression [9], and higher expression of the enzymes involved in filaggrin metabolism (such as calpain-1, caspase 14, and matriptase) [10,11] and increased Transepidermal Water Loss (TEWL) in dogs with AD [12]. The changes in ceramide content have been linked to the increased TEWL and impaired skin barrier [13]. The amount of total lipids and ceramides including all ceramide classes are significantly lower in both lesional and non-lesional skin of atopic dogs compared to normal skin, with the reduction being more severe in lesional skin [14]. Interestingly, no connection between lipid composition and predilection sites for canine atopic dermatitis lesions [12]. The awareness of decreased epidermal lipids has triggered the focus on topical application of lipid emulsions as a strategy for skin barrier repair and improvement of clinical signs [15]. Several studies have reported on the beneficial effect of topical application of ceramide-based formulations on both the restoration of lipid composition in the stratum corneum [16,17], as well as improvement of clinical signs in dogs with AD [18].

Treatment of dermatitis in dogs

There are various ways to treat dermatitis in dogs and care for your pet depending on the severity of their condition.

Parasitic dermatitis: Regular use of a prescription flea, tick and mite treatment will eliminate the majority of these problems. Unfortunately, many fleas are now resistant to supermarket products so they cannot be relied upon to treat an infestation. 95% of the flea life cycle occurs off your pet, so a household treatment will also be required. Only certain prescription products will cover mites and ticks, so be guided by your vet as to which product your pet needs. Most of these require monthly treatment, although there are some which can last up to 3 months.

Skin infections: An infection on the surface of the skin can be effectively controlled by the use of medicated shampoos. These require regular (often twice weekly or more) use initially to bring the infection under control. They can then often be reduced to once a fortnight to maintain the skin, dependent on your dog’s condition. Some dogs with deeper skin infections may require prolonged courses of antibiotics (6-8 weeks or more) to control the infection.

Allergic dermatitis: The management of this is more complex and will likely be for the lifetime of your pet. They may become allergic to more things as they go through life. If your pet is allergic to dust mites or storage mites, reducing the numbers of these within your dog’s accommodation may help. Storing food in sealed containers will reduce storage mites.

Treatment of carpeted areas, bedding for dust mites can also help, or ideally having your pet on hard floors and washing bedding regularly.

Avoiding known triggers such as grasses/pollens and washing your dog’s legs after walks can help reduce irritation.

Conducting a food trial can be worthwhile, as many dog allergies can be at least partly controlled by an appropriate diet. This involves a 6-8 week exclusion diet, using a prescription hypoallergenic diet. Nothing else must pass your dog’s lips, except water, during this time. After the food trial, you will need to gradually expose your dog to normal foods/treats to find out what the triggers are. This may not work for every dog.

Oatmeal and skin hydrating shampoos can be very useful for dogs with dry, flaky skin.

Medications to control itching — these include steroids, Atopica, Apoquel and Cytopoint. Steroids are usually used for short term management of itching as there can be long term side effects. They are usually very effective. Atopica treats the immune system cause of the itch so is useful at preventing skin infections. Apoquel is an anti-itch tablet, and in conjunction with the other measures above, can be very effective. It has fewer side effects than steroids. Cytopoint is the newest treatment available. It is given by regular injection, every 4-8 weeks and is very specific to itch, meaning it has very few side effects.

Atopic Dermatitis in Dogs: Help to Control the Itch