AllowCookies is a Boolean property that indicates if the HTTP client allows use of persistent state information using TIdCookie instances handled by CookieManager. 

AllowCookies is used when an HTTP client retrieves headers for an HTTP Response, and processes Response headers and cookie values. When AllowCookies is True, the HTTP client will ensure that CookieManager is instantiated prior to adding any TIdCookieRFC2109 or TIdCookieRFC2965 cookie instances detected in Response headers. 

The default value for AllowCookies is True, as assigned during initialization of the component.

TIdHTTP.CookieManager 

TIdCookieRFC2109 

TIdCookieRFC2965