The 37-year-old will not play while the case is investigated and is not in the squad for the four-day match against Surrey at The Oval starting today (Sunday).
Sussex confirmed: "Mitch Claydon is suspended pending the outcome of an ECB allegation of placing hand sanitiser on the ball in our match against Middlesex. There will be no further comment at this stage."
Strict protocols for matches taking place amid the Covid-19 pandemic mean players are prohibited from using saliva on the ball. That ban is extended to sweat for recreational cricket.
Rule 41.2.2 of the regulations for the Bob Willis Trophy state: "It is an offence for any player to take any action which changes or which may be perceived as likely to change the condition of the ball."
Claydon has not featured for Sussex since the alleged incident.