Etymology of “Twak”
Ayurvedic Classics used the word “Twak” or “CHARMA” for skin1.
Formation of Twak
As per view of Acharya Sushruta, the growth of skin follows the fertilization of Shukra & Shonita. In the fetal stage of development of the Garbha, the different layers of the skin are formed & this formation is caused by all the three Doshas & chiefly by Pitta2.
The formation of skin & its layers are just similar to that of formation of layers, on the top of or outer surface of boiled milk. Just as the Santaniaka, it forms in layers & gradually increase in thickness, all the layers formed in the developmental stage of the embryo of fetus join together to become the skin on the outer surface of the fully developed fetus3.
Whereas Vagbhata holds the outlook that Twaka is formed from the Rakta.
After the Paka of Rakta by Rakta Dhatwagni, it gets dried up and form the skin, line the deposition of cream in the surface of boiling milk4.
According to Acharya Charaka, the six layers of the Twaka are formed from the Mamsa Dhatu5.
There are six Bhavas (factors) which have been considered and they are responsible in the formation of Garbha. Skin is formed & nourished by Matruja Bhava.
Layers of Skin (Twacha):
There are some different opinions regarding the number of the layers of the skin (Tvacha) among the ancient Acharyas.
Maharshi Charaka has mentioned six layers of skin but only first two layers are named and rest of the four layers are counted as Producing diseases6.
Layer Contains

Udakadhara Udaka means watery substance or lymph.
Ashrukadhara Blood capillaries.
3rd Manifestation of Sidhma and Kilas.
4th Manifestation of Dadru and Kustha.
5th Manifestation of Alaji and Vidradhi.
6th Manifestation of Arunshi.

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Maharshi Sushruta has mentioned seven layers of skin along with their specific
Sr. no. Layers of Skin
Layers Thickness Reflection of disease
(in vreehi) Modern
Avabhasini 1/18 0.05 – 0.06 Sidhma, Padmini Kantaka
2 Lohita 1/16 0.06 – 0.07 Tilkalaka,Vyanga, Nyachha

3 Sweta 1/12 0.08 – 0.09 Charmadala,Ajagallika,

4 Tamra 1/8 0.12 – 0.15 Kilas, Kustha
5 Vedini 1/5 0.20 – 0.50 Kustha, Visarpa
6 Rohini 01 1.00 – 1.10 Granthi, Apachi, Arbuda,
Sleepda, Galaganda.

7 Mamsadhara 02 2.00 – 2.10 Bhagandara, Vidradhi, Arsha
name, thickness and prone origination of the disease7.

Sharangdhara also named the skin layers according to Acharya Sushruta, except that of seventh layer. He named seventh layer as “Sthoola?, the site of Vidradhi8.

Panchabhautikatva of Skin (Twaka):
Tvacha, though Panchbhautic, has Pruthvi Mahabhutadhikya9. Tvacha is the Indriya Adhisthana of Sparshanendriya and it has Vayu Mahabhutadhikya10.
All the organs are made up of Panchamahabhuta, So, Tvacha is also having
Panchabhautika constitution. As follows

Mahabhuta Effect
Prithvi Tvacha has been considered as the Upadhatu of Mamsa
Dhatu and shows that it is stable.
Jala Due to the presence of Jala Mahabhuta Tvacha is having
Snigdha and firm guna.
Agni Tvacha has the specific Varna and luster.
Vayu Tvacha is the Adhisthana of Sparshanendirya.
Akasha Presence of some micro channels of Sweda forming organ.

Ancient Term Modern Term Parts of Skin
Avabhasini Stratum corneum
Lohita Stratum Lucidum Epidermis
Sweta Stratum Granulosum
Tamra Malpighian layer
Vedini Papillary layer
Rohini Reticular layer Dermis
Mamsadhara Subcutaneous tissue
and Muscular layer
Skin and Dosha:
skin is one of the important sites of Vata and Pitta11. Skin has been considered as Adhisthana of Sparshanendirya and which is function of Vata12. Bhrajaka Pitta is located in Tvacha give luster and color to it13. Snigdhata, Slakshanata, Mruduta, Sthirata, Sheetata, Prasannata, Snigdha Varnata are the attributed to Kapha and give the luster to tvacha. For Ropana Karma (self-healing process), Kapha is most important factor.
Skin and Dhatu:
Rasa: In the context of Twak Sara Purusha Lakshana it has been also said as
Rasa Sara. 1st layer of Tvacha i.e. Udakadhara contains Rasa. So, it can be easy to understand that there is a relation between Tvacha and Rasa.
Rakta: Among the functions rakta dhatu, Varna Prasadana (provide color of skin) and Mamsa Pushti are mentioned14.

Mamsa: Twak is Upadhatu of Mamsadhatu15.
Tvacha and Mala:
Sweda: Sweda Mala of Medadhatu it is excreted by Tvacha. Sweda is responcible for maintaining the luster and humidity of skin16. Nails and hairs both are Mala of Asthi Dhatu and Twakgata Sneha is the Mala that of Majja Dhatu17.

The term Kushtha covers almost all the skin diseases. Kustha is produced due to vitiation of the seven factors i.e. 3 Doshas & 4 Dushyas 18. Due to the permutation & combination of these seven factors there is a appearance of Kustha.
Etymological Consideration:
The word ‘Kushtha’ is derived from the Sanskrit root ‘Kus Nishkarshane’ by adding the suffix ‘Tka’ to it, means ‘to destroy with certainty’, it means that which comes out from the inner part of body to the outer part.
In Ayurvedic classics, Kushtha has been classified by different views. Broadly it is classified under two main groups: Maha Kushtha and Kshudra Kushtha.
According to opinion of Acharya Charaka Kushtha are of innumerable types but for well-organized study it is classified into two major groups, 7 Mahakustha & 11 Kshudra Kushtha19.
Commentators tried to explain the difference between the main two types of Kushtha. Chakrapani has explained that Kshudra Kushtha is nothing but that of milder form of Mahakustha. Hence if the Kshudra Kushtha left untreated, it is more likely to convert in to Mahakustha20.
Dalhana explained about the word “Mahat? which means it has the ability to penetrate in to the deeper Dhatu while that of Kshudra Kushtha do not have such ability to penetrate the deeper tissue.

Sr. No Charaka Sushruta Vaghbhata
Nidana Kashyapa Bhava
Prakasha Sharangadhara
1. Kapala Kapala Kapala Kapala Kapala Kapala Kapalika
2. Udumbara Udumbara Udumbara Udumbara Udumbara Udumbara Udumbara
3. Rishyajihva Rishyajihva Rishyajihva Rishyajihva Rishyajihva Jihvika Jihvika
4. Mandal – Mandal Mandal Mandal Mandal Mandal
5. Pundarika Pundarika Pundarika Pundarika Pundarika Pundarika Pundarika
6. Sidhma – – Sidhma Sidhma Sidhma Sidhma
7. Kakanaka Kakana Kakanaka Kakanaka Kakanam Kakanaka Kakanak

8. – Aruna – – – – –
9. – Dadru Dadru – – – –

Sr. No Charaka Sushruta Vaghbhata
Nidana Kashyapa Bhava
Prakasha Sharangadhara
1. Eka kushta Eka kushta Eka kushta Eka kushta Eka kushta Eka kushta Eka kushta
2. Charma kushta Shtula rakasa Charma kushta Charma kushta Shtula raksa Gaja charma –
3. Kitibha Kitibha Kitibha Kitibha Kitibha Kitibha Kitibha
4. Vaipadik Visarpa Vipadika Vaipadik Vipadika Vipadika Vipadika
5. Alasaka Parisarpa Alasa Alasaka Vishaja Alasaka Alasa
6. Shataru Nikushta Shatarushi Shataru Shataruka Shatarva Shataru
7. Visphota Rakasa Visphota Visphota Switra Visphota Visphota
8. Dadru Sidhma Sidhma Dadru Dadru Dadru Dadru
9. Charmadala Charmadala Charmadala Charmadala Charmadala Charmadala Charmadala
10. Vicharchika Vicharchika Vicharchika Vicharchika Vicharchika Vicharchika Vicharchika
11. Pama Pama Pama Pama Pama Katchu Pama