Immunostimulant: An agent that stimulates either innate or acquired immunity.

Immunosuppressant: An agent that acts to suppress the body's natural immune response.

Instant Conditioner: A conditioner with light to intense conditioning properties that restores a healthy look and protects against further damage.

Irritant: A substance that consistently and predictably produces an adverse response (such as reddening, swelling, itching, burning, or blistering) in virtually all of the population. Irritants are not to be confused with allergens.