From Academy Bylaws:
Article III, Section 1. Membership shall be by invitation of the Board of Governors. Invitations to active membership shall be limited to those persons active in the motion picture arts and sciences, or credited with screen achievements, or who have otherwise achieved distinction in the motion picture arts and sciences and who, in the opinion of the Board, are qualified for membership.
To be considered for invitation to membership in the Makeup Artists and Hairstylists Branch of the Academy, a candidate must:
(a.i) have a minimum of seven years experience in makeup or hairstyling for theatrical feature films,
(a.ii) have supervisory position on at least five theatrical feature films (at least three within the last seven years) of a caliber which, in the opinion of the executive committee, reflect the high standards of the Academy.
(b) have been nominated for an Academy Award in the Makeup and Hairstyling category.
(c) have, in the judgment of the Makeup Artists and Hairstylists Branch Executive Committee, otherwise achieved unique distinction, earned special merit or made an outstanding contribution as a makeup artist or hairstylist.
A letter of recommendation from each sponsor must be included with the proposal.