Dilated (enlarged) pupils are one of the more visible physical signs of opioid withdrawal, and one of the items clinicians check as part of standardized withdrawal assessment.
Why it happens: Opioids constrict pupils as a direct pharmacological effect (this is why “pinpoint pupils” are a classic sign of opioid use or overdose). Withdrawal reverses this, and pupils dilate beyond their normal resting size.
What this is used for clinically: Pupil size is one of the measured items on the COWS (Clinical Opiate Withdrawal Scale), used to assess withdrawal severity in a standardized way. COWS scale article
What tends to help: No specific treatment is needed for this symptom alone; it resolves as withdrawal overall resolves or as medication for opioid use disorder is started.
Medically reviewed by [pending]. Source: SAMHSA TIP 63, COWS scale documentation.