Already used herbs
Aloe vera extract is used as a component in Ayurvedic formulations. It significantly reduced acne lesions . This Asian dermatological remedy was in accord with the therapeutic use of Aloe spp. in South Africa . However, A. vera was insignificant to suppress P. acnes-induced ROS and proinflammatory cytokines . In the same ayurvedic formulation, Azadirachta indica, Curcuma longa and Hemidesmus incidus were used for acne treatment . These herbs significantly suppressed the production of ROS induced by P. acnes . Accordingly, their anti-inflammatory activity should be stronger than A. vera, highlighting their potential in inflammatory lesions treatment.
A common spice, poultice onion (Allium cepa), was traditionally used for acne  owing to its mild keratolytic, anti-fungal and bacteriostatic properties with respect to its sulphur containing  including its anti-inflammatory flavonoids . However, its malodor limits the application as well as the possibility of irritation.
Asia is not the only continent using traditional herbs for the treatment of acne vulgaris. Centella asiatica was used as a general tonic for leprosy and wounds particularly for acne in Africa . Although its mechanism remains unknown, skin care products containing C. asiatica are widely commercialized in Asia.
Essential oils of Eucalyptus radiate and Melaleuca alternifolia commonly known as Australian eucalyptus and tea tree, respectively, have been extensively used in acne treatment . M. alternifolia oil gel was found to effectively reduce acne lesions compared with benzoyl peroxide at the same concentration but fewer side effects . Its inhibitory activity against skin flora including S. aureus, S. epidermidis and P. acnes was contributed by the major aroma components, terpinen-4-ol, α-terpineol and α-pinene . However, terpene and limonene in tea tree oil caused allergies in hypersensitive skin . Thus, caution regarding the dose used should be taken. However, adverse reaction of tea tree oil is rare. Therefore, it is one of the most popular and effective over-the-counter acne treatments . In addition, juniper (Juniperus communis) oil was also found to be effective in the treatment of acne .
Licorice or Glycyrrhiza glabra, an herb native to Asian countries, was topically applied in the treatment of acne  because of its anti-inflammatory effect . However, its anti-oxidant activity was low . In addition, Gossypium barbadense, an anti-microbial and anti-oxidant herb , was used as a folk remedy for acne in Yemen owing to its biologically active terpenoids .
Basil or O. gratissimum was used to treat acne both in combination with A. vera gel  or alone  because of the powerful anti-inflammatory activity of the containing linolenic acid .
Rosa damascene, which is mostly used as a fragrance, was found to effectively inhibit P. acnes with respect to its anti-inflammatory action . Similarly, rose oil was used in the treatment of acne . Therefore, rose should be incorporated into cosmetic products as a multifunctional ingredient. Red clover or Trifolium pretense was employed as an acne remedy because of its anti-inflame flavonoids .
Subjectively used herbs
In addition to the aforementioned herbal extracts, the following herbs have been used subjectively in acne treatment:
The anti-inflammatory effects of Roman and German chamomiles (Anthemis nobilis and Matricaria recutita) were applied in skin inflammation treatment owing to their biologically active flavonoids, particularly apigenin, α-bisabolol and chamazulene .
Comparable activity against P. acnes and S. epidermidis was found between tea tree and Abies koreana oils containing bornyl acetate, limonene, α-pinene and camphene as the main compounds. In addition to acne pathogenesis inhibition, A. koreana oil exhibited anti-inflammatory effects towards LPS, TNF, IL, NO and PG . In addition to those mentioned biologically active essential oils, S. epidermidis was found to be inhibited by Salvia sclarea (minimum inhibitory concentration; MIC = 1.5–2 mg ml−1)  and Ziziphora clinopodioides  oils. Furthermore, the essential oils of Anthemis aciphylla  and Tamarix bovena  were found to inhibit facial flora that would applicable in acne care product.
Eucommia ulmoids, a traditional tonic used in East Asia, was found to potently inhibit P. acnes (MIC = 0.5 mg m−1) and reduced the secretion of proinflammatory cytokines . Thus, this herb should be further formulated in acne care products and clinically evaluated to prove its efficacy in human volunteer.
The susceptibility of P. acnes and S. epidermidis was tested on hop (Humulus lupus)-isolated compounds, lupulones and xanthohumol. Lupulones were the most potent bactericidal compounds against P. acne and S. epidermis at a MIC of 0.1 μg ml−1, whereas xanthohumol, a strong S. epidermidis inhibitor, showed stronger anti-oxidant activity .
Jojoba liquid wax, a common ingredient of cosmetics, was found to effectively reduce neutrophil infiltration by reducing myeloperoxidase activity. Nitric oxide level was reduced as well as TNF-α release , which is appraisal for inflammatory acne treatment.
The oriental anti-inflammatory herb , Magnolia officinalis, has long been used in East Asian countries. Its magnolol and honokiol potently inhibit P. acnes and P. granulosum (MIC = 3–4 and 9 μg ml−1, respectively) with the proven anti-inflammatory effects .
Radical scavenging activities of emblica or Phyllanthus emblica were found to be appropriate for acne treatment because of its active components that were mainly ascorbic acid, gallic acid and skin whitening agents, quercetins, and ellagic acid. In particular, the isolated geraniin showed the highest activities in DPPH and lipid peroxidation assays as well as NO scavenging activity [111–114].
Biological activity assessments of Punica granatum, which is an edible fruit, were made using radical, lipid peroxidation and superoxide assays . Its anti-oxidant quality was high highlighting its capacity in the development of acne care products that have already been commercialized in Asia.
The inhibition of NO production and scavenging activity of Selginella involvens were found to be dose dependent. This herb also has an anti-inflammatory effect towards IL in keratinocytes. Furthermore, its non-antibiotic, anti-microbial potential on P. acnes has been reported and was non-cytotoxic at a concentration <50 μg ml−1 .
There were anti-inflammatory reports of Chinese medicinal plants root and leaf extracts. These include Aralia continentalis via inhibition of cyclooxygenase-2 (COX-2) and NO expression including NF-κB deactivation . Clerodendron trichotomum was found to suppress PGE2 production , which appropriates for inflammatory acne treatment.
Prevention of acne was traditionally carried out using Ayurvedic formulations containing Curcuma longa [80, 119], which have anti-bacterial and anti-inflammatory activities . This plant has long been used in Thai folk remedies for skin care and for its aromatherapy aspects in various traditional preparations, for instance masks, and compresses.
Garcinia mangostana is another economic fruit of Thailand. Its pericarp consisted of xanthones that potently inhibit P. acnes and S. epidermidis . These anti-bacterial activities were found increased in a mature fruit . Furthermore, it was found to be highly effective in free radical scavenging following P. acnes induction and suppressed the production of TNF-α, a pro-inflammatory cytokine , particularly in young fruit .
The anti-inflammatory effects of free fatty acid in sebum particularly linoleic and lauric acids were found to inhibit P. acnes . Therefore, plants containing linoleic acid may be applicable in acne lesion reduction. Sunflower (Helianthus annuus) and pumpkin (Cucurbita pepo) seed oils as well as flax or linseed oil (Linum sp.), which have a high fatty acid content mainly linoleic and linolenic acids, were incorporated into a preparation for dermatological treatments including acne . In addition to those natural oils, apricot (Prunus armeniaca), argan (Argania spinosa), avocado (Persea gratissima), baobab (Adansonia digitata), black currant seed (Rines nigrum), borage seed (Borago officinalis), cranberry seed (Vaccinium macrocarpon), corn (Zea mays), cotton seed (Gossypium sp.), evening primrose (Oenothera biennis), grape seed (Vitis vinifera), hazelnut (Corylus americana), manketti nut (Schinziophyton rautanenii), moringa (Moringa oliefera), palm (Elaesis guineensisi), poppy seed (Papaver orientale), rapeseed (Brassica napus), raspberry seed (Rubus idaeus), rice bran (Oryza sativa), safflower (Carthamus tinctorius), sesame (Sesamum indicum), soybean (Glycine soja), sweet almond (Prunus amygdalus), walnut (Juglans regia) and wheat germ (Triticum vulgare) oils, which contain more than 10% (w w−1) of linoleic acid , are used in the treatment of acne. However, evaluation of these vegetable oils in acne treatment should be performed.
Furthermore, salicylic acid that is used to remove follicular clog in acne treatment in addition to its skin peeling effect that significantly reduced comedones with less irritation than retinoids  has been found in several herbs. Salicylic acid was originally isolated from meadowsweet (Spiraea ulmaria) or Filipendula ulmaria [127, 128] including F. hexapetala  and willow (Salix alba) . Anise, bay, basil, canella, caraway, cayenne, celery, cinnamon, chilli, coriander, fenugreek, parsley, mint, mustard, oregano, paprika, pepper, rosemary, sage, turmeric and thyme are used as natural sources of salicylic acid [131, 132]. These herbs and spices in addition to fruits, for instance lemon, have been found to contain free salicylic acid in high content .
As previously mentioned, azelaic acid is an efficacious acne treatment. Therefore, herbs containing azelaic acid should be effective in the treatment of acne. Sorghum bicolor is a cereal crop that contains azelaic acid and linoleic acid in adequate yield  similar to wheat, rye and barley that contain azelaic acid.
Thus, application of these mentioned herbs is appraisal in acne care product supplying highly interest and demand in naturally derived cosmetics.