When combined with a liquid, this special form of oatmeal acts like a colloid (hence its name). This means that when molecules (the tiny particles of the grain, in this case) spread through another medium (i.e., the bath water), they permanently change the consistency of that medium (meaning that they totally mix in). The beauty of a colloidal oatmeal bath, therefore, is that the oatmeal particles don't all sink to the bottom of the tub.
To produce colloidal oatmeal, the oats themselves are very finely ground--pulverized, in fact. This enables the grain to readily absorb liquid. When the colloidal oatmeal is added to bath water, it almost instantly gives a slightly milky, almost slimy consistency to the water--which then coats the skin, moisturizing, softening, and protecting it. The emollient, or skin-softening, properties of oat products come from ingredients in the oatmeal such as cellulose and fiber.
Eczema (dry skin patches) will likely respond well to colloidal oatmeal bath treatments, as will skin conditions such as chickenpox and shingles. Insect bites, sores, and other minor skin irritations may feel soothed in such a bath, too.
If you don't mind some experimenting, you can easily try to make your own colloidal oatmeal. In a blender, coffee grinder, or food processor, finely grind the oatmeal that you purchase at the grocery store. A word of caution is warranted, however. It can be a bit difficult to determine just how fine you need to make the oatmeal before it can become a colloid in water. If it's too coarse, it will simply sink uselessly to the bottom of the tub. The commercial product is processed so minutely that its ability to form a colloid is assured.
Whether you're preparing a bath with a commercial colloidal oatmeal product or your home "grind," the instructions are the same: Draw a tepid bath. (Don't use hot water, which will further inflame the skin and absorb moisture from your skin rather than lubricating it.) Add several cups of the oatmeal to the bath as it's filling up. Soak for 10 minutes. Then pat (don't rub) your skin dry. Repeat the bath as needed, up to three times a day, depending on the severity of your condition.
If you feel sticky after the bath, try rinsing your body off with a few cups of tepid water from the faucet in your tub.
Among the widely available colloidal oatmeal bath products are Aveeno Regular Bath, Aveeno Oilated Bath, and numerous other bath preparations. Lotions, soaps, and other oatmeal-containing topical products are sold as well.
