Interesting Fact/Hint:

Alternative poultice made at home: Mustard is a great treatment for joint pain, rheumatism and neuralgia. A mustard poultice has a strong analgesic effect and brings blood to the surface, increasing circulation. The main medicinal property of mustard is it's natural and penetrative volatile oil, which has a strong odor. This oil is released when mustard powder is mixed with water, provided that water is not to hot. Never mix dry mustard with hot water. If a hot poultice is needed, mix it with cold or lukewarm water first and let it stand for a few minutes then add hot water.
A paste can be made with equal parts of flour and mustard. For sensitive skin use up to 4 parts flour and 1 part mustard. Spread the mixture on a cotton cloth and apply. Cover with a piece of flannel to retain warmth. If it is on a leg or hoof or any area that can be wrapped do so as normal poultices. Or it can be held by hand for 15 - 30 minutes.
From the book, "Equine Massage - A Practical Guide" by Jean-Peirre Hourdebaigt, RMT

For any extra information on poultices please feel free to contact me.