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Anesthetics are medications designed to help manage pain by either decreasing pain to tolerable levels or blocking pain outright, according to MedlinePlus, a service of the National Institutes of Health 4. Local anesthesia is an anesthetic that affects the specific body part where it is administered 24. This form of anesthesia does not induce unconsciousness and is usually administered via injection, although local anesthesia is also available in nasal spray and gel form 24.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.

Hemorrhaging and Infection

Local anesthesia may cause hemorrhaging or bleeding when administered via injection, notes MedlinePlus 24. The injection site may become infected. Nevertheless, the chances of excessive bleeding and infection are low, especially if the proper precautions are taken.

Impaired Mental Clarity

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Normal mental functions can become impaired by local anesthesia, notes 234. This is because local anesthesia can impede the ability to think clearly due to possible unintended psychotropic effects 24. The precise duration and degree of impaired mental clarity may vary depending on the specific local anesthesia used 24. Nevertheless, until the effects of the local anesthesia have worn off, significant decisions should be postponed 24.

Impaired Respiratory Function

Respiratory function may be impaired by local anesthesia, notes MedlinePlus 24. The specific degree to which respiratory function is impaired depends on the kind of local anesthesia used 24. The patient's medical history, local anesthesia type and dosage should be considered carefully prior to administering local anesthesia 24.

Neural Damage

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Local anesthesia may cause long-term neural damage, explains MedlinePlus; however, such a side effect is uncommon 24.

Allergic Reaction

Using local anesthesia carries the risk of a possible allergic reaction, according to the American Pregnancy Association 124. Nevertheless, the risk of this side effect occurring can be greatly reduced if factors such as medical history and patient allergies to medication are thoroughly considered prior to administering the local anesthesia 24.


Pain may not be blocked completely by local anesthesia, notes 234. The reasons for this are varied. Switching from local to general anesthesia may be necessary if the pain experienced exceeds the patient's tolerance level 24.

Prolonged Anesthetic Effects

Local anesthesia may take a longer time than expected to wear off, notes 234. This side effect depends upon the patient and type of local anesthesia used 24.

Swelling of Affected Area

Swelling may occur at the site where the local anesthesia was administered, according to the American Pregnancy Association 124.

Temporary Impaired Movement

Local anesthesia can impair movement and the overall utility of the affected area, notes MedlinePlus 24. The muscles in the affected area may be unresponsive and may even feel weaker than usual.