Superficial and deep soft scars and atrophic scars may do well; these are scars which  can  be  easily  stretched and have little or no fibrosis. Ice-pick scars, deep fibrotic scars and keloids do not benefit. Unfortunately many patients have multiple scars which are of various sorts so that only a small and insignificant number may be helped with bovine collagen.

 

  If bovine collagen is a possible treatment then it is necessary  to know whether or not the patient or a relative has a history of organ-, or nonorgan-,  specific autoimmune disease. Patients with a history of ulcerative colitis or Crohn's disease are also contraindicated. If there is no contraindication a test  dose is given intradermally in the forearm to  exclude any hypersensitivity to the bovine collagen and read at  six weeks. Positive reactions are  uncommon , with an incidence of 1 per cent. HLA studies have shown that most patients who develop  a reaction  lack the HLA DR4 antigen. Attempts to  preselect adverse reactions by examining circulatory antibodies to bovine collagen after the test dose are  not successful.

  Assuming that the  test is negative the injection is given intradermally, aiming to overcorrect the deficiency by one-and-a-half times.  The collagen contains lignocaine  and is relatively well tolerated.  A minimum of three injections is given at monthly intervals and if no improvement is seen at this stage further injections are unnecessary. Assessment of such therapy is not  easy and  subjective assessment is usually more favourable than results obtained by objective assessment such as that using photographs. Soft scars  and mixed scars do best. Ice-pick  and fibrotic scars  respond badly.

 

  Until  recently this author's department only  had experience  with Zyderm I  (35 mg/ml).   Zyderm  II (65 mg/ml) and Zyplast (75 mg/ml) should be available soon  in the UK and may possibly give better results. The injection is more than just a filler. The use of monoclonal antibodies to monitor human and bovine collagen has shown that bovine collagen is replaced by human  collagen over a period of sixteen weeks.13 Bovine collagen is very expensive and is probably only used in private practice and more specialized dermatology units. However, since the method is relatively free of side-effects,  it  is  well  within  the  scope  of  any Fibrotic dermatologist. The main side-effect is the rare development of a granulomatous reaction at the site of injection despite a negative skin test. Because of this very rare event, it is not wise to treat all the scars at the same time.