Psychologically, there could also be something going on for itchy horses. Are they happy in their situation? with their herd? Ask them.
Laya still itches but less badly now. She itches more when she is bottom of the pecking order in one herd than when she is top of the order in the other.
That is a good point Andi, my Irish DraughtX gelding is what I would call a highly sensitive horse. He suffers from sweet itch, dust allergy and suffered a mild attack of laminitis. Sometimes he breaks out in hives he has very sensitive skin ( he is palomino )and a very sensitive nature, easily upset and becomes over aroused and stressed. During times of stress he develops a cough and the sweet itch bothers him more,
He is 19 years now and over the years I have used lots of different remedies for him. In his case herbs and food additives did not help, neam oil painted on his mane and tail daily was a great help.
For the past couple of years he has worn a Boett rug and that really worked for him. However this year Gouch has shredded the rug all in the name of play. At the moment I am dabbing oil of eucalyptus on his mane and tail and that seems to be working.