Insulin lispro, sold as the brand Humalog, is a synthetic and fast-acting form of insulin primarily used to treat Type 1 diabetes. Doctors typically prescribe it along with a long-acting form of insulin. Humalog also may be used by people with Type 2 diabetes along with oral medications. Like other forms of insulin, you inject Humalog with a needle and syringe or with an insulin pump. Although rare, some individuals may experience an allergic reaction to Humalog insulin.
Caution
Because Humalog works quickly, you should use it within 15 minutes before or just after you eat a meal or it may cause low blood sugar, according to the website Drugs.com. Low blood sugar, or hypoglycemia, is the most common side effect of Humalog. Symptoms of hypoglycemia may include headache, dizziness, drowsiness, weakness, tremors, nausea, confusion, difficulty concentrating, sweating, blurred vision and rapid heartbeat. The condition can become life-threatening if not resolved. Carry sugared hard candy or glucose tablets with you while you use Humalog so you have something sweet to consume if you begin experiencing low blood sugar.
Local Allergic Reaction
As with any insulin injection, you could experience a local allergic reaction to Humalog. Symptoms may include redness, itching, swelling, heat or nodules under the skin. These are typically minor reactions that begin early in therapy and clear up within a few weeks; however, some people need to discontinue Humalog due to localized allergic reactions. A poor injection technique rather than an allergy also can cause these symptoms.
Systemic Allergic Reaction
A systemic allergic reaction to Humalog insulin is less likely but much more serious. Signs may include an itchy rash that may spread over your entire body, hives, wheezing, difficulty breathing, chest tightness, muscle pain, rapid heart rate, sweating, low blood pressure, faintness, and facial or mouth swelling. An allergic reaction to Humalog requires emergency medical attention because it can lead to life-threatening anaphylaxis.
Incidence
A true allergy to insulin is rare, affecting between one in 1,000 to one in 10,000 people, according to the website NetDoctor. In clinical studies, 30 of 2,944 patients receiving Humalog developed itching, with or without a rash, compared with 17 of 2,969 receiving regular human insulin, as detailed by Drugs.com. Drugs.com explains that sensitization reactions, or those which develop with continued use, are usually connected with animal proteins in insulin.
