Final answer:
Central sensitization in chronic pruritus can occur in both humans and other mammals, leading to increased sensitivity and lingering itchiness. The hygiene hypothesis proposes that increased allergies in developed countries may result from overly sterile environments that lack pathogens, causing the immune system to react to harmless allergens. David's itchy wound, following an animal bite and foreign travel, calls for further medical assessment for hypersensitivity or infection.
Step-by-step explanation:
The concept of central sensitization in chronic pruritus is not exclusive to humans; this physiological process can occur in other mammals as well. It refers to the increased sensitivity of the nervous system, which leads to an exaggerated response to stimuli, such as itch or pain. This process can contribute to the persistence and intensity of pruritus over time.
In David's case, a 45-year-old journalist with symptoms that include pruritus at the site of a dog bite, there is potential concern for an infection or a hypersensitivity reaction. The negative culture and sensitivity tests rule out a bacterial infection. Moreover, his travel history and the fact that the wound is now presenting with itching sensations might lead to consideration of other diagnoses, such as a type I hypersensitivity or a zoonotic infection.
Development of allergies in more developed countries has been linked to over-cleanliness according to the hygiene hypothesis. This theory suggests that the immune system, which evolved to deal with pathogens, may overreact to harmless substances as allergens in the absence of pathogenic challenges, leading to an increase in allergic responses.