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Itchiness & the Microbiome - It’s all connected

Author: DVM Dana Hogg

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 in their feet, ears, arm pits, and facial regions. Therapy is aimed at reducing pruritus and treating any secondary bacterial or fungal skin infections. In cases where certain foods are the culprit, limited ingredient or hydrolyzed protein diets can be curative. In cases where environmental allergens are involved, it can be a little more challenging. There are drugs such as steroids and certain biologics designed to reduce itching. Allergy immunotherapy is also an option – this therapy is aimed at improving 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 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 Lactobacilllus 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 3 weeks of age until 6 months of age. Both groups were topically exposed to dermatophagoidies farinae, a common house dust mite. Blood samples were collected routinely and intradermal allergy testing was performed at 6 months of age. 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 the addition of probiotics may help decrease some immunological indicators associated with atopic dermatitis and patients may be able to have a reduction in certain medications when receiving probiotics. These studies suggest that probiotics may serve as a good complementary treatment in atopic dermatitis.

  • Marchegiani, Andrea, et al. “Impact of Nutritional Supplementation on Canine Dermatological Disorders.” Veterinary Sciences, vol. 7, no. 2, 2020, p. 38. Crossref, doi:10.3390/vetsci7020038.
  • Oshima-Terada, Yuri, et al. “Complementary Effect of Oral Administration of Lactobacillus Paracasei K71 on Canine Atopic Dermatitis.” The Japanese Journal of Veterinary Dermatology, vol. 19, no. 3, 2013, pp. 155–58. PubMed, doi:10.2736/jjvd.19.155.
  • Kim, Hyejin, et al. “A Double-Blind, Placebo Controlled-Trial of a Probiotic Strain Lactobacillus Sakei Probio-65 for the Prevention of Canine Atopic Dermatitis.” Journal of Microbiology and Biotechnology, vol. 25, no. 11, 2015, pp. 1966–69. researchgate, doi:10.4014/jmb.1506.06065
  • Marsella, Rosanna, et al. “Evaluation OfLactobacillus Rhamnosusstrain GG for the Prevention of Atopic Dermatitis in Dogs.” American Journal of Veterinary Research, vol. 70, no. 6, 2009, pp. 735–40. Crossref, doi:10.2460/ajvr.70.6.735.

Dr. Dana Hogg graduated in 2015 from North Carolina State University. She grew up in Wilson, North Carolina. Growing up with several animals, Dr. Hogg was drawn to the field of veterinary medicine at a young age. She completed her undergraduate degree at NCSU in 2009 and her master's degree in 2011.

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