Gel

A gel (coined by 19th-century Scottish chemist Thomas Graham, by clipping from gelatine) is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state. By weight, gels are mostly liquid, yet they behave like solids due to a three-dimensional cross-linked network within the liquid. It is the crosslinking within the fluid that give a gel its structure (hardness) and contribute to the adhesive stick (tack). In this way gels are a dispersion of molecules of a liquid within a solid in which the solid is the continuous phase and the liquid is the discontinuous phase.

Gel: Nonfluid colloidal network or polymer network that is expanded throughout its whole volume by a fluid.

Note 1: A gel has a finite, usually rather small, yield stress.

Note 2: A gel can contain:

Note 3: Corrected from ref., where the definition is via the property identified in Note 1 (above) rather than of the structural characteristics that describe a gel.

Preparation H

Preparation H is a brand of medications made by Pfizer, used in the treatment of hemorrhoids. Hemorrhoids are caused at least in part by inflamed blood vessels, and most versions of Preparation H work by reducing inflammation in blood vessels.

The company that makes this product incorporated in 1926 as American Home Products (AHP) and "one of AHP's earliest prizes was the acquisition of a sunburn oil in 1935 that the company transformed into Preparation H, which became one of the world's best-selling hemorrhoid treatments." AHP changed its name to Wyeth in 2002, and was then bought by Pfizer in 2009, which was reported to have paid $68 billion.

Formulations

Several formulations have been produced. For example, some are in a water-based gel, while some are petroleum jelly-based, and the suppositories use a base of cocoa butter. It can come as a suppository, or as a medicated wipe. The active ingredients range from simple moisturizers with witch-hazel astringent to preparations containing drugs such as phenylephrine, pramoxine, and hydrocortisone. Formulations available vary from one country to another.