The County Tipperary trainer has had his hearing on possession of anabolic steroid charges adjourned until March 20, the week after Cheltenham, but punters should proceed with care regarding backing his other contenders.
Those include Cheltenham Gold Cup third favourite Last Instalment as well as Dunguib, a leading fancy for the Coral Cup.
The BHA have said that even if the samples taken come back negative, Fenton's runners are not guaranteed to be allowed to run at Prestbury Park.
Blood samples will be taken as well as hair samples, which trace any potential drug use back over a far longer period. The results will be available next week.
Fenton has already lost a key member of his Festival team when owner Barry Connell scratched The Tullow Tank saying none of his horses in the care of Fenton would run until proceedings had finished.
Paul Bittar, chief executive of the BHA, said: "Following the adjournment of the court case, we want to take steps which serve to uphold public confidence in the relevant races at the Cheltenham Festival and the sport in general.
"The testing of the Fenton-trained horses will form a part of the decision making process as to how best to achieve this objective."
Eddie O'Leary, brother of Ryanair owner Michael and racing manager for Gigginstown House Stud, owners of Last Instalment, said: "We wrote to the BHA today to ask them to come and test Philip's horses, so it is what we wanted.
"We have absolutely nothing to hide and hopefully this will help clear a few things up.
"When Philip was raided it was January 2012 - Last Instalment won the Moriarty in February 2012 and was tested afterwards, that came back clean. The BHA is more than welcome to come over."
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