Dermal reactivity to histamine, serotonin and bradykinin in relation to allergic skin reactions of the horse.

This study investigates how horse skin reacts to the introduction of histamine, serotonin, and bradykinin, comparing these responses to reactions produced by insect allergens. The researchers also tested the effects of two anti-histamine drugs on these reactions.

Investigating Skin Reactivity

• The study analyzed the reactivity of horse skin to intradermal (within or between the layers of the skin) inoculation of histamine, serotonin, and bradykinin. These three substances are commonly associated with allergic reactions and inflammation.
• The reactions were then compared to those caused by a 1% whole-body extract of Culicoides, a genus of biting midges known to cause allergic reactions in horses.
• While both histamine and bradykinin led to significant reactions, the study found no strong correlation between the skin’s response to the insect allergen and either histamine or bradykinin. This highlights a potential discrepancy in the mechanisms behind different types of allergic reactions.

Testing Anti-histamine Drugs

• Two anti-histamine drugs, promethazine hydrochloride and tripelennamine hydrochloride, were tested for their ability to reduce allergic reactions to the insect extract. Anti-histamines work by blocking the action of histamine, a key player in the body’s response to allergens.
• The results demonstrated that both drugs were effective in diminishing the allergic reaction triggered by the midge extract. This suggests that these treatments could be used to manage horses’ allergic responses to insects.

Implications and Further Research

• Despite the findings of this study, the difference in response between the chemical allergens and insect extract calls for further research. Understanding this difference better can shed light on the underlying mechanisms of varying allergic reactions.
• The effectiveness of the two anti-histamine drugs suggests they could be useful in managing such allergic reactions. However, their long-term efficacy and safety need to be further evaluated.