Question: What's the judgment of touching the hair of the Prophet for blessings?
Answer: Bismillah, praise be to Allah the creator of all creations, the creator of the cause and results and the creator of the harm and benefit, and may Allah raise the rank of Prophet Muhammad and protect his nation from which he fears for it,
Know that all Muslims seek blessings from the Prophet's traces whether by kissing his hair, or part of his traces such as his clothes or his grave or his Minbar podium. It's confirmed in Sahih al-Bukhariy that our Prophet when he made his hajj, he shaved his hair and distributed it to the companion, and the purpose was for them to seek blessings from it and not to eat it! because hair is not edible, rather they kept it and sought blessings from it. Also the companions used to take the clothes of the Prophet and put them in water and use that water for blessings and as a cure for the sick by the will of Allah. Because our Prophet is full of blessings. It's also confirmed that the companions used to place their hands on Handhala whom the Prophet had blessed with his hand, and so they used to touch the place where the Prophet's hand was seeking blessings from the trace of the Prophet's hand. This is all confirmed in the authentic Sunnah, and is clear evidence that it's permissible.
Some people claim out of ignorance consider such acts as shirk blasphemy, but that's due to their extrem blindness and ignorance.
Imam Ahmad bin Hanbal himself was asked about touching and kissing the minbar of the Prophet for the blessing and about seeking the blessing by visiting the grave of the Prophet. He responded by saying: "This matter is not prohibited," as was narrated by ^Abdullah, the son of Imam Ahmad, in his book titled Al-^Ilal wa Ma^rifat ur-Rijal.
Imam Ahmad also said it was a liked thing to make tawassul by the Prophet when there is drought. Furthermore, Imam Ahmad said that blessings would descend on those present in a session when the name of Safwan Ibn Sulaym (Safwan Ibn Sulaym was a pious man at the time of the salaf.) was mentioned. How can Ibn Taymiyah and his followers (wahhabis) claim to follow the school of Imam Ahmad? Imam Ahmad is in one valley and they are in another valley altogether.
So do seek blessings Tabarruk by touching and kissing the hair of the Prophet and do not hesitate, because Allah creates the blessings and the benefit and no one else. This is the way of Ahlus-Sunnah, and those who stray will be heading to hellfire.
Allah knows best.