Permanent hair dyes are commonly used in over the counter direct to consumer products and within hair salons. Allergy, also known as contact dermatitis, to hair dye is a well known phenomenon. Herein, we seek to decrease the risks of allergy to hair dyes by testing a novel version of p-phenylenediamine (PPD) with less allergy potential.

For patients with PPD sensitizations, it is important to find alternatives for dark hair dyes. P-toluenediamine (PTD) and potentially also 2-methoxyethyl p-phenylenediamine (ME-PPD) show cross-reactivity with PPD and therefore we want to prove that our new compounds PPD-6 and PPD-7 show no or significantly reduced cross-reactions with PPD and do not induce relevant allergic reactions in patients with proven PPD sensitizations.

Our specific aims for this study are the following:

A1) To show that PPD 6 and PPD 7 have reduced or optimally no reaction in standard patch tests in patients with proven allergy to PPD A2) To compare the sensitization pattern to other possible commercially available alternatives for hair dye, such as ME-PPD and PTD A3) To evaluate and rule out any possible non-specific irritant reaction of PPD-6 and PPD-7 in these patch tests (i.e. confirm in-vitro safety profile in-vivo)

Inclusion Criteria:

- Proven Diagnosis of PPD and/or PTD sensitization (patch tests and clinically relevant eczematous reactions to hair dye)

Exclusion Criteria:

• Use of oral immunosuppressive, anti-inflammatory and chemotherapy medications, particularly corticosteroids for at least 1 month before testing.
• Immunocompromised patient (e.g. Cancer, Diabetes mellitus, medication, Immunodeficiency, radiation therapy)
• History of acute hepatitis, chronic liver disease or end stage liver disease.
• History of human immunodeficiency virus (HIV) or acquired immune deficiency syndrome.
• Use of illicit drugs within the past 6 months prior to study start and/or opioid use disorder.
• Pregnancy as established by questionnaire

Adults with sensitivity to PPD and/or PTD