According to an ICRC press release,
Since Mr Shalit's capture in June 2006, the ICRC has repeatedly asked Hamas to allow the exchange of Red Cross messages between Gilad Shalit and his family. The most recent requests were made at the highest level, but these and all others have been refused.
Repeated requests by the ICRC to visit Gilad Shalit to ascertain his conditions of detention and treatment have also been refused. Visiting people deprived of their freedom and enabling them to exchange personal news with their relatives is one of the ICRC's main humanitarian tasks. In 2008, the organization visited nearly half a million detainees in 83 countries, including nearly 36,000 who were registered and monitored individually.You can read the full press release here.