When applied topically, Advil, an over-the-counter pain reliever, may still cause some side effects due to its active ingredient ibuprofen being absorbed into the body (DrugPatentWatch.com) [1].

Common side effects associated with topically applied ibuprofen, such as Advil, include:

Skin irritation, redness, or rash in some individuals, particularly after prolonged application or when applied to broken skin [3].
Allergic reactions are rare, but may involve hives, itching, swelling, or increased heart rate [4].
Stinging, burning, or itching sensations at the application site, which usually resolve after discontinuing use [5].

In addition, some users may be more sensitive to the effects of topical ibuprofen, such as an increased risk of kidney damage in individuals with pre-existing kidney issues [6].

If irritation persists or is severe, individuals should discontinue use and consult a healthcare professional.

It is essential to note that the risk of side effects might be lower with topically applied products compared to oral administration, but this largely depends on factors such as product concentration, method of application, and individual skin conditions.

Sources:

[1] https://www.drugpatentwatch.com/
[3] https://www.webmd.com/drugs/2/drug-1046/admiral-ibuprofen-topical/details
[4] https://www.medlineplus.gov/druginfo/meds/a682633.html
[5] https://www.everydayhealth.com/drugs/advil-topical
[6] https://www.everydayhealth.com/drugs/advil-side-effects.htm