Itchiness & the Microbiome -  It’s all connected

The skin is the largest organ of the body for both humans and companion animals. It is one of the first lines of defense against the external environment. Dermatological issues in companion animals are a common cause of veterinary visits. A particularly common skin issue is called Atopic Dermatitis, which is a chronic inflammatory condition resulting from exposure to an allergen. This exposure causes the release of certain cells in the immune system which results in an allergic reaction that clinically manifests as pruritus, also known as itchiness. Both environmental and dietary sensitivities can cause atopic dermatitis.

Atopic Dermatitis & the Microbiome:

Atopic dermatitis typically affects animals' feet, ears, armpits, and facial regions. Treatment plans aim to reduce pruritus and address secondary bacterial or fungal skin infections. In cases where certain foods are the culprit, limited ingredient diets or hydrolyzed protein diets can be curative. It can be a little more challenging in cases where environmental allergens are involved. There are drugs such as steroids and certain biologics designed to reduce itching. Allergy immunotherapy is also an option – the goal of this therapy is to improve the immune system to reduce the effects of allergens.

Treatment Studies:

The gut microbiome regulates the intestinal barrier and integrity. It helps provide protection from pathogens and aids in immune modulation. The skin and gut both share a connection with the external environment. While the relationship is not fully understood, many studies confirm there is a bidirectional relationship between gut and skin health [1].

One study examined the effects of Lactobacillus paracasei K71 supplementation in dogs with atopic dermatitis. The control group received cetirizine, an antihistamine, while the trial group received Lactobacillus paracasei K71. Participants were allowed to continue any medications currently being used for the  management of atopic dermatitis. Each individual was assigned a medication score. Clinical signs during the study were scored based on a canine atopic dermatitis extent and severity score system. While the study did not reveal significant improvement in pruritus scores between the groups, the group receiving Lactobacillus paracasei K71 had a slightly lower score than the control group. The study also determined that the dogs receiving Lactobacillus paracasei K71 had a reduction in medication scores over time compared to the control group suggesting that the supplementation of probiotics may help reduce the amount/dose of medications used to control atopic dermatitis [2].

A different study examined the effects of Lactobacillus sakei probio 65 administration to dogs with diagnosed atopic dermatitis. It concluded that there was a significant decrease in disease severity in dogs receiving Lactobacillus sakei probio 65 [3]. The reaction of the immune system to certain allergens drives the development of atopic dermatitis. One cell commonly activated in allergies is called IgE (immunoglobulin E).  

Another study evaluated the effects of Lactobacillus rhamnosus strain GG when administered to puppies. It involved breeding two adult beagles with atopic dermatitis twice (the litters were one year apart). The first litter was the control group. The second litter was administered Lactobacillus rhamnosus from three weeks of age until six months of age. Both groups were topically exposed to dermatophagoidies farinae, a common house dust mite. At six months intradermal-allergy-testing was performed, and blood samples were collected routinely. The litter that received Lactobacillus rhamnosus had “significantly lower levels of serum titer IgE and a milder reaction to intradermal testing.” While there were no significant changes in clinical signs associated with atopic dermatitis between the groups, there is evidence that probiotics may reduce some immunological factors associated with atopic dermatitis [4].

Probiotic Studies Conclusion:

Treatment of atopic dermatitis can be challenging and lifelong. While more studies are warranted, there is evidence that probiotics may help decrease some immunological indicators associated with atopic dermatitis. They may also be able to reduce consumption of certain medications when receiving probiotics. The studies examined in this blog suggest that probiotics may serve as a complementary treatment for atopic dermatitis.