Is ida the parasympathetic nervous system?

The comparison is common and roughly apt in mood, but it is an analogy from a later century. The classical descriptions are about temperature, mental state and nostril flow, not about nerves.

When should I practise left-nostril breathing?

When you are hot, agitated or trying to wind down. It is a poor choice first thing in a sluggish morning, where the right-nostril practice fits better.

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Principal channel

Ida

Iḍā · इडा

The left channel, winding around sushumna from the base of the spine and ending at the left nostril. Cool, lunar, receptive, and the half of the pair that most modern life underuses.

left moon cooling receptive

Runs from: The left side of muladhara
Runs to: The left nostril
Ends at: Ajna, where it meets pingala
Quality: Cooling, lunar, chandra
Governs: Rest, reflection, receptivity
Paired with: Pingala

The lunar side

Ida is drawn winding around the central channel, crossing it at each centre, and terminating at the left nostril. Its qualities are consistently cool: the moon, night, the colour white, water, and the mental states that go with them.

In the texts it is also called chandra nadi. Practices that emphasise it, left-nostril breathing in particular, are prescribed for heat, agitation and difficulty sleeping.

Nostril dominance

Nasal airflow alternates from one side to the other over a period of roughly an hour or two in most people, which physiology calls the nasal cycle. The yogic literature noticed this long before it was measured and built an entire diagnostic practice on it, swara yoga, which reads the dominant nostril as a guide to what kind of activity suits the moment.

Left dominance is read as a time for quiet work, taking in rather than putting out.

Working with it

Chandra bhedana, breathing in through the left nostril and out through the right, is the direct practice. A few minutes is enough to notice a change in temperature and pace. It is the standard recommendation for the end of the day, and the one to skip if you are already sluggish.

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Its pair

Pingala

The solar channel on the right.

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Between them

Sushumna

The central channel the two are meant to open.

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Where it ends

Third eye chakra

Ajna, the meeting point of the three.

Frequently asked questions

: The comparison is common and roughly apt in mood, but it is an analogy from a later century. The classical descriptions are about temperature, mental state and nostril flow, not about nerves.
: When you are hot, agitated or trying to wind down. It is a poor choice first thing in a sluggish morning, where the right-nostril practice fits better.