Ayyoub's blog has posted criticism of the government
Rami Siyam, who blogs under the name of Ayyoub, was detained along with three friends after leaving the house of a fellow blogger late at night.
No reasons have been given for Mr Siyam's detention. The other friends were released after being questioned.
Human rights groups have accused Egypt of eroding freedom of speech by arresting several bloggers recently.
BBC Arab Affairs analyst Magdi Abdelhadi says blogging in Egypt is closely associated with political activism in a culture where democratic freedoms are severely restricted.