In this paper, an interference relay channel where two independent sources communicate with two destinations by the help of a relay is studied. The relay is full-duplex and employs decode-forward type strategy. Using Carleial's rate splitting where each source transmits common messages to be decoded at both destinations and private messages for the desired destination, an achievable rate region is obtained. The relay decodes both common and private messages and transmits them cooperatively with the sources to the destinations. For the symmetric Gaussian interference relay channel, the results show that the maximum rate sum is achieved when the relay helps the sources in the transmission of common messages only. Moreover, unlike the regular interference channel, when the relay is present, the sources continue to transmit common information even when the interfering links can support much less rate than the direct links.