Summarize:

Saddle soap can be used to clean horse tack and other leather products such as shoes and boots. However, saddle soap should not be used on every leather-based product. There are a variety of different types of leather used in products. Different types require different cleaners and the only way to know whether saddle soap is okay is to consult the manufacturer's directions. If you don't have the directions handy, you can google the product name and find information online about cleaning and care. If you see any warnings about saddle soap, it might be better to go with a different cleaner. Lye is a highly caustic compound found in many commercial brands of saddle soap. If lye is listed as a primary ingredient on the brand of saddle soap you've selected, you might want to ditch that product and look for an alternative brand. Lye's caustic nature mean it's particularly hard on leather products. It absorbs moisture quickly, which can dry out leather causing it to crack, split, and otherwise deteriorate faster. Saddle soap made with lye also has a high pH level, which causes leather to harden and darken. It can be difficult to get lye-heavy saddle soap out of cracks and crevices if you're cleaning tack, resulting in a crusty white residue. Opt for making your own saddle soap or try to buy homemade saddle soap from a local farmer's market. While such products do use lye, they tend to use it in reasonable amounts that will cause minimal damage to leather. You can make inexpensive saddle soap in your own kitchen. This might be a better option than buying commercial saddle soap, as the products used can be harmful to leather. Use protective gloves throughout the cooking process. You'll be handling lye, which is a pretty heavy-duty material. You want to make sure you avoid burning your skin. Use an apron to cook, as lye should not come into contact with clothes you wear regularly. Get your ingredients. You'll need two pots, made of stainless steel or heat-resistant glass, a stainless steel spoon, and some kind of jars or boxes to store the concoction. You will also need beeswax, pure flake lye, castile soap shavings, water, and pure gum turpentine. These products can be purchased at grocery stores, hardware stores, and health food stores. In one pot, combine 6.25 parts beeswax, 10 parts pure flake lye, and 10 parts water. Boil the mixture for 5 minutes, stirring constantly. Get the second pot. Melt together 2 parts castile shavings and 10 parts water. Once the soap liquifies, add it to the first mixture. Move the pot away from heat and add 15 parts turpentine. Pour the mixture into containers, cover, and store the saddle soap in a cool and dry part of your home. The soap does not have a shelf life, so you can wait as long as you want to use it. When you finish, clean your kitchen thoroughly. Keep your protective gloves on during this time. Lye can be harmful if ingested, so you want to make sure your kitchen is clear of lye before you begin cooking and eating again.
Read the manufacturer's directions. Avoid lye heavy products. Make your own saddle soap.