S00.421A Blister (nonthermal) of right ear, initial encounter

Billable ICD-10-CM code, FY2026.

Built from S00.421 with 7th character A (initial encounter).

Applies from S00 Superficial injury of head

Excludes1 (never code together)

• diffuse cerebral contusion (S06.2-)
• focal cerebral contusion (S06.3-)
• injury of eye and orbit (S05.-)
• open wound of head (S01.-)

7th character note

• The appropriate 7th character is to be added to each code from category S00

7th character required

• A — initial encounter
• D — subsequent encounter
• S — sequela

Code annotations containing back-references to S00.421A

Back-references to S00.4

• Type 2 Excludes: S09.3 Other specified and unspecified injury of middle and inner ear ("injury to external ear (S00.4-, S01.3-, S08.1-)")

Back-references to S00

• Code Also: G96.00 Cerebrospinal fluid leak, unspecified ("head injury (S00-S09)")
• Code Also: G96.08 Other cranial cerebrospinal fluid leak ("head injury (S00 - S09)")
• Code Also: G96.09 Other spinal cerebrospinal fluid leak ("head injury (S00 - S09)")
• Code First: R65.1 Systemic inflammatory response syndrome (SIRS) of non-infectious origin ("injury and trauma (S00-T88)")

Nearby codes

• S00.419A Abrasion of unspecified ear, initial encounter
• S00.419D Abrasion of unspecified ear, subsequent encounter
• S00.419S Abrasion of unspecified ear, sequela
• S00.42 Blister (nonthermal) of ear
• S00.421 Blister (nonthermal) of right ear
• S00.421A Blister (nonthermal) of right ear, initial encounter (this code)
• S00.421D Blister (nonthermal) of right ear, subsequent encounter
• S00.421S Blister (nonthermal) of right ear, sequela
• S00.422 Blister (nonthermal) of left ear
• S00.422A Blister (nonthermal) of left ear, initial encounter
• S00.422D Blister (nonthermal) of left ear, subsequent encounter