Sayyiduna Imran bin Husayn (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "Ruqyah is for the evil eye or for the sting of a venomous creature."
The Shaykh says: That is, and Allah knows best, these two are the most deserving of ruqyah because of the greater harm in them; and al-humah is the venom of venomous creatures.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19589