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Other actives

Bis-aminopropyl diglycol dimaleate

Also listed as bond builder, bond repair, maleic acid bond treatment

The patented 'bond-building' active in popular repair treatments. Hair does look and feel better; the claim that it rejoins broken bonds inside hair is unproven.

Limited evidenceTypical strength: Concentration not usually disclosed; highest in salon pre-treatments and masks

What it is

Bleaching and colouring break disulfide bonds, the cross-links that give hair strength. This ingredient, a maleate salt, is claimed to react with the broken ends and link them back together, and it is sold as a pre-treatment during bleaching and as an at-home mask, shampoo and conditioner.

Independent lab analysis of bleached hair treated with maleate-type repair agents found a smoother, more intact-looking surface but no increase in disulfide bonds and no direct sign of the claimed cross-linking.

How strong is the evidence?

Limited evidence

Evidence consists mainly of manufacturer lab testing (breakage and strength measurements). An independent spectroscopy study of maleate-type repair agents found cosmetic surface improvement but no evidence of rebuilt bonds. There are no controlled trials on real-world breakage.

What it's used for, checked

Hair feels smoother and stronger after bleaching

Mixed

Surface improvement is seen in the lab; whether breakage falls in real use has not been independently tested.

Rebuilds broken disulfide bonds

Unproven

Not shown in independent structural analysis.

Makes bleaching safe for any hair

False

It may reduce damage; over-processed hair still breaks.

Works well with

  • keratin

Who should be careful

  • Generally well tolerated.
  • Bleaching chemicals are the main risk to hair and scalp; a bond treatment does not make repeated heavy bleaching safe. Stop if the scalp burns.

The studies

Every citation is checked against its PubMed record.

  1. Structural investigation on damaged hair keratin treated with alpha,beta-unsaturated Michael acceptors used as repairing agents.
    Di Foggia M, Boga C, Micheletti G, Nocentini B, Taddei P · Int J Biol Macromol · 2021 · Laboratory study (spectroscopy on bleached hair)

    On bleached hair, maleate- and shikimic-acid-based repair agents changed the cuticle and cortex and made the surface smoother, but none increased disulfide bonds in the cortex, and nothing directly showed the claimed cross-linking reaction.