Different types of special cleansers have been developed for people with different skin types. Acne cleansers are more suitable for oily skins to prevent breakouts, but they may overdry and irritate dry skin. Very dry skin may require a creamy lotion-type blemish prone cleansers, as long as it doesn't make skin feel oily afterward. These are too gentle to be effective on oily (or even normal) skin, but dry skin requires much less cleansing power. Some cleansers may incorporate fragrance or essential oils. However, for some people these cleansers may irritate the skin and often provoking allergic responses. Using a special cleanser to remove dirt is considered to be a better alternative to bar soap or another form of skin cleanser not specifically formulated for the face for the following reasons: Bar soap has a high pH (in the area of 9 to 10), and skin's natural pH is 5.5. This means that soap can change the balance present in the skin to favor the overgrowth of some types of bacteria, exacerbating acne. Bar cleansers in general, soap or not, have thickeners that allow them to assume a bar shape can clog pores, leading (once again) to acne. Using bar soap on the face can remove natural oils from the skin that form a barrier against water loss. This causes the sebaceous glands to subsequently overproduce oil, which may again lead to clogged pores. Conversely, in order to prevent drying out the skin, many blemish prone cleansers incorporate moisturisers. Moisturisers are a complex mixture of chemical agents specially designed to make the external layers of the skin (epidermis) softer and more pliable, by increasing its hydration (water content). Naturally occurring skin lipids and sterols as well as artificial or natural oils, humectants, emollients, lubricants, etc. may be part of the composition of commercial special cleansers. They usually are available as commercial acne cleansers and blemish prone cleansers for cosmetic and therapeutic uses, but can also be prepared at home using common pharmacy ingredients. Besides imparting or restoring normal levels of hydration to the skin, special cleansers can have several additional intended and unintended effects on its users, including building a barrier against the loss of water through the epidermis, repairing scaly, damaged or dry skin resulting from external environmental aggressions or internal changes (such as in acne or naturally dry skin), repairing or postponing the aging effects on the skin, etc. Many users would recommend special cleansers that are gentle, non-irritating, thoroughly cleanse skin and allow the eyelids to be washed without hurting. Additionally acne cleansers that splash away without the use of a washcloth may be preferred as cloths can harbour bacteria. Among the manufacturers that produce cleansing creams and milks as well as other special cleansers, namely acne cleansers and blemish prone cleansers, the Lancome trademark should be mentioned as one of the leading ones in this sphere of health and beauty industry. Special cleansers act on the most external of the skin layers, the so-called corneal stratum (stratum corneum, the anatomical term in Latin), which is largely formed by squamous cells or keratinocytes (an epithelial layer which is quite dynamic, i.e., it is being constantly shed and replaced by the growth of new cells coming from the deeper layers of the skin, therefore its name). Most, if not all, agents present in moisturizers are unable to penetrate these deeper layers such as dermis and hypodermis.