Panchabhautikatwa– Vayu + Agni Mahaabhoota

Lakshana-
irritates or agitates tongue after contact
Feeling of Daha or burning sensation in the mouth cavity
Causes lacrimation
Leads to watering of nose

Guna –
Veerya- Ushna
Vipaka- Katu
Vinshati Guna -Laghu,Ruksha,Teekshana,Ushna.
Doshakarma
Vitiate (Prakop) Vata-Pitta by its Ruksha,Laghu, Teekshna guna and Vayu-Agni dominance.
Alleviates (shaman) Kapha by its ruksha,tikshna and laghu guna

Functions-

कटूर्गलामयोदर्दकुष्ठ अलासकशोफजित /व्रनावासादानः स्नेहमेदः क्लेदोपशोषानः /
दिपनः पाचानो रुच्यः शोधानो अन्नस्य शोषण:/छिन्नाती बंधांन् स्त्रोतांसी वीवृणोति काफापहः // अ.हृ.सु १० /१८

Vaktrashodhana-It removes the coating over the mouth cavity which is formemaded due to Kapha or Aama by its Tikshna,ushna guna. The action of cleasing of mouth cavity is called as Vaktrashodhana .

Deepana-Pachana. Being tikshna,ushna it helps in deepan pachana kriya.Hence in Arochaka and Agnimandya, Katurasa can be used. It of Agni- Vayu Mahaabhoota. So it is Agneya in nature.This quality helps in agnideepana by increasing pachaka Pitta So in Pittakshaya, it is advised to use Katurasa.

Bhukta- shoshana-The word ‘Bhukta’ means ingested food and the word ‘Shoshana’ means ‘to absorb’. Katurasa kindles Agni which helps in digestion of food properly. Agni or Pitta is responsible for digestion of Aahara and also helps in absorption of the end result of digestion that is Aahararasa.

Ghranasrava-Ghrana means Nasal cavity. Nasa is a site of Kapha and Prana.Vitiation of Kapha dosha results in accumulation of kapha dosha in nasal cavity and produce diseases like Pratisshaya. Ushna-Teekshna guna of katurasa melts or liquefies Kapha to relive such conditions.

Ashana-rochana– Deepana-Pachana guna of Katurasa helps in proper digestion of aahara and this will helps in proper perception of taste that is Rochana. Katurasa is always used in Samavastha to help proper digestion.

Kandu-vinasha- Kandu is one of the Lakshana of Kaphadosha. Ruksha-laghu guna of katu rasa destroy the Picchila,Sthira and Styana guna of Kapha which causes Kandu.

Vrana-avasadana-The action in which increased or edematous Mansadhatu over Vrana or wound is scraped is termed as Vranavasadana. Agni-Vayu Mahaabhoota in katu rasa helps in scraping action.

Shonitasanghata bheda.- Katurasa is having the dominance of Agni-Vayu Mahaabhoota which breaks or disintigrates this Sanghata or accumulation. Teekshna -Ushna attributes help to perform this action.The meaning of Bheda is to break or to rupture. So Katurasa destroyes this sanghata.

Marga-vivarana– Marga means strotas.Agneya nature of Katurasa performs this action of Strotovivarana.

Krumi vighata – Krumi are commonly seen in wet ,moist and warm i.e kledayukta places and environment.Katurasa is used for Apakarshana or Prakrutivighata. The term Apakarshana means physical expulsion of Krumi.Ushna tikshna guna along with ruksha and katu vipak of Katurasa helps in Kleda Shoshana and formed environment in which krumi can not survive or prapogate.

Alasakadinashana– The vyadhi Alasaka is formed due to Aama. Distrubence in jatharagni leads to formation of aama dosha.Agneya nature of katu rasa ignite the atharagni and helps in proper digestion of food.Another reason of weakn agni is dominance of kapha dosha in person ,katurasa is kaphashamak in nature.hence in alsaka katu rasa used.

Shvayathu– Vitiated Pitta-KaphaRakta obstruct the pathway of Vata which futher leads to obstruction and throws Pitta etc. beneath the outer Twak or skin and Mansa results in formation of swelling called as Shvayathu or Shotha. Agneya ature of Katurasa helps to destroy this obstruction and to free the pathway of Vata and relieves Shotha. But Katurasa is not given in Pitta or Rakta pradhana shotha due to its Aagneya nature.

Upachaya-nashana-vitiated kapha leads to increase in Mansa-Medadi Dhatu qualitatively which is termed as Upachaya. Katurasa scrapes these Dhatu by its agneya guna.

Udarda-nashana-Udarda is a Kaphavikara according to Charaka. Madhavakara also mentioned ‘Udarda’ roga as kaphadhika vicar and Katurasa is uttam kaphashamaka hence it should be given in udar roga.
Katu rasa not only promotes the jatharagni but promotes the dhatwagni also which are important t digest waste products or malapachana
Chakshu-virechana- Chakshu means eyes.Eye is TejaMahaabhoota pradhan organ. So it is always advised to protect it from Kaphadosha which can damage or harm it due to Prithvi-Aapa dominance.Katurasa helps to melt Kapha which covers Chakshurindriya. This concept or action is named as ‘Chakshu-virechana’.

Indriya-sphota– Agneya nature of Katurasa destroys different Aavarana or coating due to Kapha on Indriya.It is termed as Indriya-sphotana.

Atiyoga of Katu rasa
Atiyoga of katu rasa leads to thirst,sukrakshaya (oligo spermia),loss of body sthrength,tremours,pain in back and lumbar,murccha (giddiness) and sankocyh.