When should a bug bite be seen by a doctor?

Bug bite: Should be seen if area has intense pain, increasing area of redness after first 2 days, pus draining from it, development of tightness in throat or swelling of tongue/lips, shortness of breath, general feeling of systemic illness such as high fever or extreme fatigue, tics on for more than 24 hours with rash that develops, or for just reassurance that nothing more serious than a bug bite.

If its a simple flea: or mosquito bite with no complications and topcial OTC hydrocortisone works well to clear then you don't need to see doctor. but if there is excess swelling, redness, pain, numbness, or crusting or you think it may be a spider or tick bite, if you have been hiking or traveling. then see doctor within 24 hours

For...: Swelling > 4". Or for signs of infection- ^'ed swelling, warmth, redness, purulent drainage, ^'ed tenderness or pain, red streak or fever. Or if it accompanied by nausea, vomiting, fever, generalized aches & pains with tissue loss at site.

Signs of infection : You should consult a physician if signs of infection are developing. Worsening redness, swelling, pain, increased warmth to area and fever are signs of infection and may suggest the need for further treatment, including antibiotics.