Possible Clues:

• 'Gesundheit' elicitor
• Expulsion of air from the nose
• Sound of sign of the cold (6)
• Unravelling Zen, see an involuntary reaction
• What a blow for 30 across
• Nasal eruption
• The South gets cold knees, by the sound of it
• Nasal eruption - starting a cold?
• Nasal explosion?
• Blow that where one knows the sound comes from