Mayonnaise, often shortened to mayo in casual use, is a creamy emulsion of egg yolks, oil, salt, lemon juice and mustard. Some mayonnaise recipes call for vinegar in place of lemon juice, or various gourmet oils such as olive oil or safflower oil. The ingredients are blended until the egg yolk and oil form a stable suspension of fat globules. Mayonnaise has been a staple of French cooking for centuries, but only became commercially available in the United States in 1905.

There are any number of uses for mayonnaise, many of which have little to do with its appeal as a food. Perhaps one of the most common uses for mayonnaise is as a condiment for sandwiches, along with ketchup, mustard and relish. Many sandwich meats are very lean, which may improve their flavor but do little for the overall 'mouth feel' of the sandwich. A layer of mayonnaise spread across the bread provides moisture and the satisfying feeling of fats. Mayonnaise as a condiment works well on hamburgers, cold cuts and deli sandwiches.

One of the other uses for mayonnaise is as a base for salad dressings or sauces. Adding pickle relish, chopped onions or cabbage to mayonnaise can create a good tartar sauce for fish dishes. Blending ketchup and relish with mayonnaise yields a decent Russian dressing for Reuben sandwiches. Mayonnaise can also be used as a binder for cold salads such as chicken, tuna or seafood salads. More elaborate sauces may call for a mayonnaise base with additional herbs and spices heated in a saucepan.

Over the years, consumers have developed other uses for mayonnaise. Some prefer mayonnaise to ketchup as a dipping sauce for french fries, known as potato chips outside of the United States. Mayonnaise is also used in certain fruit dips, after a bit of sweetening has been added. It is not unusual to find containers of mayonnaise alongside ketchup and mustard in European bistros and cafes.

Once you leave the confines of the culinary world, there are a surprising number of uses for mayonnaise. What follows is a short list of possible uses for mayonnaise one may not have considered until now.

1. Mayonnaise can be used as a natural hair conditioner. Massage a quantity of mayonnaise into your hair, much in the same way as a normal post-shampoo conditioner. Cover your head with a shower cap and allow the mayonnaise to remain on your hair for several minutes. Rinse thoroughly and the result should be shinier and softer hair.

2. Use mayonnaise as a facial cleanser. Apply a layer of mayonnaise as you would a deep cleansing facial soap. After 15 or 20 minutes, wipe off the mayonnaise and rinse your face thoroughly. The oils and salt of the mayonnaise will restore moisture and remove impurities.

3. In case of a sunburn emergency, apply cold mayonnaise to the affected area. The coolness of the mayo will reduce the pain and the oil will provide much-needed moisture.

4. Some physicians are now recommending the use of mayonnaise to combat head lice infections. Certain strains of head lice have become very resistant to the traditional chemical treatments, but leaving mayonnaise in the hair overnight with a shower cap will cause the lice to suffocate and die. Comb out any remaining nits with a fine tooth comb and repeat the process seven days later.

5. Lubricate stubborn rings with mayonnaise. If a ring becomes too tight to remove, try applying a generous amount of mayonnaise to the entire finger, especially under the ring itself. Mayonnaise is very slippery, so it should reduce the friction well enough to allow removal of the ring.

6. Remove bumper stickers and residue with mayonnaise. A layer of mayonnaise applied to the remnants of a bumper sticker should soften the paper and dissolve the glue after several minutes.