Application site reactions are reactions to medical treatments which occur at the site of application. An example is skin reactions to transdermal patches.

These reactions may be caused by:

  • Irritant (non-allergic) reactions — the most common type, caused by direct skin irritation from adhesives, solvents, or the drug itself..
  • Allergic reactions — usually allergic contact dermatitis, a delayed hypersensitivity immune response to an allergen such as patch adhesive, excipients, or the active drug.
  • Mechanical forces

Some application site reactions are neither allergic nor irritant in immunologic terms, but result from friction, occlusion, pressure, or repeated removal trauma.

  • Local inflammatory injection unrelated to allergy

Implants may trigger localized redness, swelling, pain, or induration due to nonspecific inflammation rather than allergy.

See also