Single most likely diagnosis
- Allergic reaction: This is often the most common reason for waking up with a swollen lip, possibly due to an allergic reaction to something ingested or exposed to before bedtime, such as food, medication, or an insect bite.
Other Likely diagnoses
- Angioedema: A condition characterized by the rapid swelling of the skin and mucous membranes, which can be caused by allergies, genetics, or other factors.
- Insect bite or sting: An overnight insect bite or sting could cause lip swelling.
- Trauma: Unintentional self-inflicted trauma during sleep or an unnoticed injury could lead to lip swelling.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Anaphylaxis: Although less common, anaphylaxis is a severe, life-threatening allergic reaction that requires immediate medical attention. Swelling of the lip could be part of the initial presentation.
- Hereditary angioedema: A rare but potentially life-threatening condition that causes recurring episodes of severe swelling.
Rare diagnoses
- Melkersson-Rosenthal syndrome: A rare neurological disorder characterized by recurrent, often unilateral, facial paralysis or weakness, swelling of the face and lips, and the development of folds and furrows in the tongue.
- Ascher's syndrome: A rare condition characterized by the combination of double lip, blepharochalasis (excess skin of the eyelids), and nontoxic thyroid goiter, which could potentially cause lip swelling.