Any person may submit a written complaint to the department charging a license holder or applicant with unprofessional conduct and specifying the grounds for the charge. If the director determines that the complaint merits investigation, or if the director has reason to believe, without a formal complaint, that a license holder or applicant may have engaged in unprofessional conduct, the director shall investigate to determine if there has been unprofessional conduct. A person who files a complaint under this section in good faith is immune from suit in any civil action related to the filing or contents of the complaint.