hypertrophic scarring is caused by an imbalance between extracellular matrix ( ecm ) protein deposition and degradation . there are many factors affecting surgical scarring such as healing of the wounds , tension , and the line of the scars . prolonged redness and post - inflammatory pigmentation of the scar tissues cause patients to be concerned about the noticeability of scars , especially in aesthetic surgery such as lower blepharoplasty , face - lift , or breast augmentation . apart from the use of advanced wound dressing products to accelerate wound healing , many methods are used to prevent scar formation . pressure garments , taping , and silicone gel have been prescribed for scar prevention ; however , these methods have not been prescribed for the reduction or prevention of post - inflammatory hyperpigmentation , which is a common problem in patients with fitzpatrick type iv or v skin [ 35 ] . it has previously been shown that herbal extracts have various effects in scar - remodeling pathways and might have scar - reduction properties [ 6 , 7 ] . the combined herbal extract gel ( chg ) is a composition of allium cepa ( 12% w / w ) , centella asiatica ( 5% w / w ) , aloe vera ( 4% w / w ) , phyllanthus emblica ( 1.5% w / w ) , and tamarindus indica ( 1.5% w / w ) extract . this formulation was developed as it was believed that their synergistic effects would help in the prevention of scar development [ 8 , 9 ] . only one randomized control study has been done to evaluate the efficacy of chg in preventing surgical scarring . thus , the purpose of this study was to evaluate the efficacy of the chg in the prevention of surgical scar formation . patients aged over 18  years , who were fitzpatrick type iii or iv skin , and had under gone bilaterally symmetrical surgical procedures at siriraj hospital ( bangkok , thailand ) were enrolled in the study . patients with critical illnesses ( such as systemic infections or hemodynamic instability ) , major - acute illnesses , or chronic medical illnesses that can affect wound healing ( such as bleeding disorders , transplantation , diabetes , obesity , cancer , chronic renal failure , and hematologic diseases ) were excluded from the study . pregnant patients and patients with allergic reactions to chg were also excluded from the study . all procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation ( institutional and national ) and with the helsinki declaration of 1975 , as revised in 2000 and 2008 . the placebo gel was a combination of water , acrylate , c10 - 30 alkyl acrylate crosspolymer , polysorbate 20 , and fragrance , and was similar in color and consistency to that of the chg . the containers were labeled a or b. the identity of the gels was kept blind to the evaluator ( second investigator ) and the patients . one week after the sutures were removed , random cards were withdrawn for each site of the scars to indicate which containers ( a or b ) would be applied on the sites , chg on one scar and placebo on another scar . application of the gels was done twice daily , once in the morning and once in the evening . during each follow - up visit , the scars were photographed and evaluated using patient and observer scar assessment scale ( posas ) [ 1013 ] . evaluations were done on the 2nd , 4th , 8th , and 12th week after commencing application of the gels . the assessment consisted of the two numeric scales : the patient scar assessment scale ( psas ) , which was completed by the patient , and the observer scar assessment scale ( osas ) , which was completed by one observer [ 11 , 14 ] . the median of the total score of the posas was analyzed using the wilcoxon paired signed - rank test method twenty patients with fitzpatrick type iii or iv skin , classified as beige to beige - with - brown tint skin color , were enrolled in this study ; however , only 17 patients completed the follow - up period . the average age of the patients was 39.44  years and ranged from 18 to 64  years . most of the surgical procedures in our study involved excision of nevus at both arms . the other operations were intercostal drainage of median sternotomy at the subcostal area ( 2 cases ) and mandibular osteotomy at both angles of the chin ( 1 case ) . the dimensions of the scars included in this study varied from 3 to 10  cm.table  1demographic datademographic data 
 n ( % ) sex ( n  =  17 )  female13 ( 76)operation ( n  =  20 )  lower blepharoplasty5 ( 25 )  excision ( excision of mole and excision of lipoma)6 ( 30 )  liposuction4 ( 20 )  breast surgery2 ( 10 )  others ( icd drainage of median sternotomy and mandibular osteotomy)3 ( 15 ) 
 icd intercostal drainage 
 icd intercostal drainage the chg - treated scars showed lower psas scores compared with the placebo group in color , stiffness , thickness , irregularity , and overall scores with statistical significance at 12  weeks follow - up ( p value 0.03 , 0.04 , 0.03 , 0.04 , and 0.02 , respectively ; figs .  1 , 2 ) . the scores in pain and itching in the chg group did not significantly differ from the placebo group at 12  weeks ( p value 0.72 and 0.33 , respectively ) . the scars in the chg group showed lower osas scores compared with the placebo group in pigmentation , thickness , and overall scores at 12  weeks ( p value 0.04 , 0.04 , and 0.04 , respectively ) . the osas scores in vascularity , relief , and pliability in the chg group were significantly less than those in the placebo group at 8  weeks ( p value 0.03 , 0.04 , and 0.04 , respectively ) . the efficacy of chg compared to placebo gel is demonstrated in figs .  3 and 4.fig .  1patient scar assessment scale score comparison between combined herbal extracts gel ( chg ) and placebo group at 2 , 4 , 8 , and 12  weeks follow - upfig . 2observer scar assessment scale score comparison between combined herbal extracts gel ( chg ) and placebo group at 2 , 4 , 8 , and 12  weeks follow - upfig . 3a 30-year - old female patient underwent excision nevus at both arms . at 8 weeks follow - up , psas for chg and placebo groups were 15 and 21 , respectively , and osas for chg and placebo groups were 14 and 23 , respectively . at 12  weeks follow - up , psas for chg and placebo groups were 12 and 19 , respectively , and osas for chg and placebo groups were 12 and 21 , respectively . chg combined herbal extracts gel , osas observer scar assessment scale , psas patient scar assessment scalefig . 4a 40-year - old female patient underwent bilateral breast reduction . at 4  weeks follow - up , psas scores for the chg and placebo groups were 29 and 32 , respectively , and osas scores for the chg and placebo groups were 21 and 28 , respectively . at 12  weeks follow - up , psas scores for the chg and placebo groups were 21 and 21 , respectively , and osas scores for the chg and placebo groups were 21 and 22 , respectively . chg combined herbal extracts gel , osas observer scar assessment scale , psas patient scar assessment scale patient scar assessment scale score comparison between combined herbal extracts gel ( chg ) and placebo group at 2 , 4 , 8 , and 12  weeks follow - up observer scar assessment scale score comparison between combined herbal extracts gel ( chg ) and placebo group at 2 , 4 , 8 , and 12  weeks follow - up a 30-year - old female patient underwent excision nevus at both arms . at 8 weeks follow - up , psas for chg and placebo groups were 15 and 21 , respectively , and osas for chg and placebo groups were 14 and 23 , respectively . at 12  weeks follow - up , psas for chg and placebo groups were 12 and 19 , respectively , and osas for chg and placebo groups were 12 and 21 , respectively . chg combined herbal extracts gel , osas observer scar assessment scale , psas patient scar assessment scale a 40-year - old female patient underwent bilateral breast reduction . at 4  weeks follow - up , psas scores for the chg and placebo groups were 29 and 32 , respectively , and osas scores for the chg and placebo groups were 21 and 28 , respectively . at 12  weeks follow - up , psas scores for the chg and placebo groups were 21 and 21 , respectively , and osas scores for the chg and placebo groups were 21 and 22 , respectively . chg combined herbal extracts gel , osas observer scar assessment scale , psas patient scar assessment scale the longest period of wound healing is the maturation phase . in this phase , surgical scars are hypervascularized , raised , and hard for 23  months after the wound has healed if we can reduce or shorten these signs and symptoms , the patient will benefit . patients with fitzpatrick type iii skin or above have a greater chance of developing post - inflammatory hyperpigmentation , hypertrophic scarring , and keloids than patients with fitzpatrick type i and ii skin . many methods have been described for scar prevention , such as pressure garments , taping , and silicone gel sheets / ointment ; however , these methods have not been described for controlling post - inflammatory hyperpigmentation and the other symptoms experienced during the maturation phase . silicone is believed to improve scarring via wound hydration and increased static charge [ 1618 ] . these mechanisms effectively decrease the stimulation of keratinocytes , reduce cytokine production , and inhibit excessive collagen synthesis . silicone also helps to rearrange the collagen fibers during the wound healing process via the polarization between the silicone and skin . it has previously been demonstrated that silicone has benefits in scar reduction [ 1821 ] . the silicone in a gel preparation is easy to use when compared with conventional silicone gel sheeting . combination of the silicone derivative with other active compounds , such as onion extract ( which have various mechanisms ) , may also have synergistic effects in scar prevention [ 6 , 24 ] . allium cepa ( onion ) extract , the main component of chg , is useful in reducing neoangiogenesis in hypertrophic scars and keloids , resulting in the clinical improvement of skin vascularity [ 7 , 2427 ] . it shows an anti - inflammatory effect by inhibiting lipopolysaccharide - induced tumor - necrosis factor - alpha ( tnf- ) production . reported that onion extract could fade scar color and the most effective therapeutic results were produced when it was combined with silicone gel sheet treatment . several scientific reports have documented that centella asiatica has the ability to enhance wound healing . by treating with centella asiatica extract , the maturation of the scar is stimulated by the production of type i collagen . the treatment also results in a marked decrease in the inflammatory reaction and myofibroblast production [ 30 , 31 ] . asiaticoside , the active ingredient of centella asiatica , has an anti - scarring effect by decreasing the transforming growth factor beta-1 expression and enhancing the expression of inhibitory smad-7 [ 30 , 32 ] . aloe vera is widely used as a traditional herbal medicine in many countries and is effective in the treatment of wounds . some studies have shown that aloe vera extract increases the rate of healing by enhancing keratinocyte multiplication and migration , the expression of proliferation - related factors , and epidermis formation [ 33 , 34 ] . the study by vzquez et al .   reported that aloe vera could interrupt cyclooxygenase enzyme ( cox ) function and decrease the production of eicosanoid . therefore , the combined extracts of allium cepa , centella asiatica , and aloe vera may encourage an anti - inflammatory effect . saponin significantly stimulates angiogenesis by modifying the balance of protease / protease inhibitor secretion in human endothelial vascular cells [ 3638 ] . phyllanthus emblica extract has antioxidant potentials as well as antimicrobial activity which can be a good therapeutic agent for accelerating the wound healing process [ 39 , 40 ] . tamarindus indica extract and phyllanthus emblica may , therefore , have an additive effect in reducing hyperpigmentation . in the results of our study , the color , stiffness , irregularity , and overall scores in psas and pigmentation , thickness , and overall scores in osas of the chg study group showed improved scores at 12  weeks . the scars might have less chance to develop post - inflammatory hyper - pigmentation . in this study moreover , the sample size is quite small and there are many other variables that may affect the outcomes . further studies with larger sample sizes and longer term follow - ups are needed to confirm the benefit of this product . combination of herbal extracts gel might be effective in the prevention of surgical scar formation . all procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation ( institutional and national ) and with the helsinki declaration of 1975 , as revised in 2000 and 2008 . this article is distributed under the terms of the creative commons attribution noncommercial license which permits any noncommercial use , distribution , and reproduction in any medium , provided the original author(s ) and the source are credited .