Sorry to burst your fairy bubblle! ...but using Fairy Liquid in the short term may not do any damage, but it is a detergent, containing sodium lauryl sulphate which is a commercial degreaser used to strip car engines and clean factory floors, also parabens which have been found to be carsonagenic (cancer forming)  These are also present in many commercial shampoos, but in lesser form.  The degreasers are an irritant and under testing have caused cararacts.  It may get the grease out of your horse, but could seriously irritate the skin underneath, leaving it vulnerable to flying insects.  Please research SLS and Parabens on the internet.  I don't even use it on myself and my kids anymore.  For a fantastic horse shampoo I can seriously recommend Mukout solid shampoo. It contains Indian neem oil which is a natural pesticide and used to keep flying insects away. Neem also has natural anti-bacterial and anti-septic benefits. Unlike commercial shampoos it contains no SLS or Parabens which can irritate and dry the skin, often making skin conditions worse, and cleans with amazing results!  The website is www.mukout.com

 I've worked on various event yards... all of which have used fairy liquid, johnson's baby shampoo, or tesco's apple shampoo!! Only if you're showing and need white-as-white horses would I bother with horsey shampoos.