This simple touch switch circuit diagram is using IC CD4011 that wired as a flip-flop. IC CD4011 is a CMOS IC, mean that this IC require very low current for controlling its gates. Pin 9 and 13 are work as the set and reset, since them connected to the positive via R1 and R2, the logic gates of the IC will be in high state. When pin A and B are connected (touched by hand), the gate of the IC will be closed and output become low. This switches ON the transistor Q1 and activate the relay gates. When we touch trough pin C and D, the gates again become high and switches the transistor OFF and make the relay OFF also. By touching those pins, the relay can be switched ON and OFF. This circuit using 12V DC as a power, the relay can be a 12V, 200 ohm SPDT relay.
source : www.circuitstoday.com