Can Weather Changes Increase Itchiness?

Hello, Summarians!

I found this report on weather changes and pruritus intriguing. Intuitively, we seem to recognize that season changes affect itching, but it is nice to have some real evidence. What do you think?

Please give me feedback on ways I can make it more useful to you.

If it is valuable to you please consider sending it on to a friend 😄 

Weather and Atopy in Dogs

This study investigated the relationship between environmental pollen concentrations, weather conditions, and pruritus in dogs with canine atopic dermatitis (cAD), a genetic and environmentally influenced inflammatory skin disease. It focused on dogs sensitized to pollen allergens, as identified by intradermal testing (IDT), and explored the correlation between pollen levels, weather factors, and clinical signs of cAD. 

The key findings include: 

Relative Humidity was significantly correlated with pruritus, likely due to its effect on aeroallergen release from pollen grains. This aligns with similar findings in humans. 

Air temperature, rainfall, and sunshine hours had no impact on pruritus, despite their influence on pollen production and dispersal. 

Airborne pollen concentration did not show a direct correlation with pruritus scores in these dogs, differing from some findings in human studies. 

Medication scores correlated with pruritus, reinforcing the idea that increased pruritus prompts higher antipruritic drug use. 

The study highlighted the need for careful interpretation of IDT results, as the pollen traps used may not reflect true pollen exposure for dogs, especially given urban factors and indoor living. It concluded that while humidity significantly influences pruritus, airborne pollen concentration may not be a reliable predictor of allergic flare-ups in cAD. Further research is needed to assess real pollen exposure in different environments. 

Widorn L, Zabolotski Y, Mueller RS. A prospective study evaluating the correlation between local weather conditions, pollen counts and pruritus of dogs with atopic dermatitis. Vet Dermatol. 2024; 35: 500–507. https://doi.org/10.1111/vde.13268 

Bottom line — Humidity does influence pruritus.

Liposomal Bupivicaine in Horses

Liposomal bupivacaine (LB) was developed to provide prolonged postoperative analgesia and reduce opioid use, with FDA approval for use in dogs and cats for specific procedures. It has been studied for use in horses, but its efficacy and pharmacokinetics remain less clear. 

In horses, LB's effectiveness for prolonged local anesthesia has been explored, with varying results. Studies have indicated that LB can reduce lameness for longer than traditional bupivacaine hydrochloride (BH), but the duration of its effect falls short of the 72 hours anticipated. Research shows that a higher dose of LB is necessary to achieve lameness elimination compared to BH. Despite higher doses, LB's analgesic effect was not consistently effective, and it did not always eliminate lameness in horses. 

Pharmacokinetics studies indicate that LB has a lower peak plasma concentration compared to BH but maintains a higher concentration at later time points. The decline in plasma levels of LB is more rapid than in some other species, possibly due to differences in liposome breakdown or increased clearance in horses. 

Overall, LB has shown promise for extended analgesia but falls short of ideal duration in horses, with its effectiveness and dosing needing further investigation.

McCarrel, T. M., Cole, C., Maxwell, L. K., Roe, H. A., & Morton, A. J. (2024). Bupivacaine and liposomal bupivacaine do not produce prolonged perineural anesthesia in a lameness model and are detectable beyond clinical effect in conditioned Thoroughbreds. American Journal of Veterinary Research (published online ahead of print 2024). Retrieved Sep 6, 2024, from https://doi.org/10.2460/ajvr.24.06.0167 

Bottom line — It doesn’t last as long as hoped.

Patch Testing for Food Allergies in Dogs

Adverse food reactions (AFR) in dogs encompass both allergies and food intolerances. Food allergies involve an immune response, which may be immunoglobulin E (IgE)-mediated, cell-mediated, or both, triggered by a component in the food. AFR is often suspected in dogs with chronic, nonseasonal pruritus, regardless of gastrointestinal signs, which may include diarrhea, vomiting, and flatulence. An elimination diet (ED) using novel or hydrolyzed proteins is used to diagnose AFR, with improvements seen within eight to thirteen weeks. A food challenge can confirm AFR if clinical signs recur after reintroducing the previous diet.

Testing for AFR remains challenging, as there is no definitive test besides the ED trial. While serological tests and skin prick tests are used in human medicine to detect food sensitization, they do not confirm food allergy. For dogs, patch tests have recently been introduced, particularly for those with chronic pruritus. These tests, however, are mainly useful in identifying foods unlikely to trigger reactions. A combination of prick and patch tests has been explored, showing a moderate level of sensitivity and specificity, with the two tests identifying different allergic mechanisms. The prick test had a specificity of 75% and a positive predictive value of 81.8%, while the patch test showed a higher sensitivity (70%) but lower specificity (50%).

The study revealed that 76% of dogs with chronic pruritus improved on an ED, suggesting AFR as a significant factor in chronic pruritus. Chicken and pork were common allergens in prick and patch tests. While the tests are helpful in guiding ED formulations, they should be used together to improve diagnostic accuracy. AFR is likely underdiagnosed, and its prevalence in dogs with nonseasonal pruritus may be higher than previously thought. For a more accurate diagnosis, it is recommended that EDs be maintained for at least eight weeks, with prick and patch tests used to inform food choices for the diet.

Possebom, J., Cruz, A., Gmyterco, V.C. and de Farias, M.R. (2022), Combined prick and patch tests for diagnosis of food hypersensitivity in dogs with chronic pruritus. Vet Dermatol, 33: 124-e36. https://doi.org/10.1111/vde.13055

Bottom line — Shows some promise but needs further study.

Just putting things in perspective …