Hi Welcome Healthcare Magic.....
Itchiness at the rectal area could be commonly due to a fungal infection
, because the moisture around the area favours fungal growth and infection.
Can it be a STD
possible ?? if you are practising anal intercourse and you are the receiver.
To confirm whether its a STD or a fungal infection you need to consult a physician who can send the swab from the area for culture and sensitivity.
Fungal infection - can try clotrimoxazole-hydrocortisone
ointment for a local application.Candid-B ointment.