How is the allergen introduced in intradermal testing?

Intradermal testing is a specific method used to identify allergic responses, particularly for instances where skin prick tests may not provide sufficient sensitivity. The process involves injecting a diluted allergen directly into the dermis, which is the layer of skin situated just beneath the outer epidermis. This method allows for a controlled introduction of the allergen, leading to a localized immune response if the patient has an allergy to that specific substance.

The reason this method is effective is that it places the allergen in closer proximity to the immune cells present in the dermis, thus facilitating a quicker and more accurate assessment of the patient's allergic sensitivity. The response usually manifests as a localized swelling or reaction at the site of injection, which can be measured for the evaluation of the allergic response.

While the other methods mentioned are indeed used for allergy testing, they do not employ the same technique as intradermal testing. For instance, applying a diluted allergen to the skin typically refers to patch testing or prick testing, which are not as invasive and may not penetrate the skin to provide the same level of detail regarding sensitivities. Scratching the skin or using a nasal spray introduces allergens in ways that do not focus exclusively on the intradermal response, thus making